EM hãy giải thích tại sao khi cắt cành bưởi chiết đen trong phai cắt bớt phiến lá và không trong giữa trưa

cho tam giác ABC vuông tại A, trên cạnh BC lấy điểm D sao cho BD= BA. Gọi I là trung điểm của ÀD. a,CM: BI là phân giác của góc ABD. b, AC cắt BI tại K, CM: KD vuông góc với BC. c, DK cắt AD tại H, CM: KH= KC. d,CM: ADsong song với HC

tại sao nói có cấu tay quay con trượt đương nối với nhau bằng những khớp quay và khớp tịnh tiến

giúp minh với 30 câu trắc nghiệm thôi . Mai mình thi rồi (30 điểm ) nhanh nhưng đúng nha 21. These two novels are both very interesting.______ one should I buy? A. What B. Which C. Where D. Who 22. _________ it rains a lot in winter, I still love walking the dog in the park in this season. A. Because B. As C. Although D. However 23. Excuse me, ______ is the staff room? I want to speak to Miss Lily. A. When B. What C. Which D. Where 24. You'd better take an umbrella ________ it is going to rain. A. so B. because. C. although D. and 25. ________ do you go to school? - Five days a week. A. How often B. How much C. How many D. How long 26. George didn't want to get up late, ____ he set the alarm clock to go off at 6.30. A. but B. and C. so D. for 27. __________ do you look like the most in your family? A. Which B. Who C. What D. Where 28. I was crossing the road _________ the bus arrived at the station. A. while B. because C. when D. as long as 29. ____ of your classmates are going camping with you? A. How often B. How much C. How many D. How old 30. The car is very old, __________ it is reliable A. but B. and C. so D. because Choose the underlined part that needs correcting in each sentence below. 31. Million of children around the world enjoy Walt Disney animated films. A. Million B. around C. enjoy D. animated 32. The Wingless Penguin is on at 8 o'clock Friday night, in the Disney channel. A. is B. on C. at D. in 33. Phong is going to a book exhibition with his parents last Friday. A. is B. a C. with D. last 34. The most popular TV channels in Vietnam is VTV1 and VTV3, which are very informative and interesting. A. the B. is C. which D. informative 35. Who is more intelligent than grade 5 students? is a popular TV series which can both entertain as well as educate a young audience. A. is B. series C. as well as D. a IV. READING Read the passage and decide whether the sentences are True (T) or False (F). There's a lot of good stuff on TV, so I watch something most days of the week. It's the easiest thing to do when I get home from work and I’m too tired to go out or read a book. I watch quite a lot of documentaries and the news because I like to know what's happening in the world, and I'm also a big fan of reality shows like Big Brother. In Big Brother they get real people together in a house for a few weeks, and because the house is full of cameras you can watch how they behave. Sometimes the people are celebrities. As a viewer you can decide which of the people you don't like, and then vote to evict them from the house - I love that! (Source: insideout.net) T F 36. The writer often enjoys watching TV. 37. It is hard to watch TV for relaxation. 38. Documentaries and news programmes are often outdated. 39. All reality shows must involve famous people. 40. Viewers can make a decision of who can stay in Big brother. Read the following passage and choose the option (A, B, C or D) that best answers each of the questions below. At the beginning of TV history, there were several types of TV technology. One system was a mechanical model based on a rotating disc. (Rotating discs are discs that spin like CDs.) The other system was an electronic model. In 1906, Boris Rosing built the first working mechanical TV in Russia. In the 1920s, John Logie Baird in England and Charles Francis Jenkins in the United States demonstrated improved mechanical systems. Philo Taylor Farnsworth also showed an electronic system in San Francisco in 1927. His TV was the forerunner of today's TV, which is an electronic system based on his ideas. Now TV is everywhere. Before 1947, there were only a few thousand televisions in the U.S. By the 1990s, there were televisions in 98% of American homes. (Source: englishforeveryone.org) 41. Rotating means A. going up and down. B. going back and forth. C. spinning. D. staying still 42. Who invented the mechanical TV model? A. Boris Rosing B. John Logie Baird C. Charles Francis Jenkins D. Philo Taylor Farnsworth 43. Which of the following statements is wrong? A. More than one TV technology was developed in the history. B. Nowadays TV is a popular household equipment. C. John Logie Baird and Charles Francis Jenkins invented an electronic TV based on the previous mechanical one. D. No inventors mentioned in the passage came from Asia. 44. Whose invention is the current TV mostly based on? A. Boris Rosing B. John Logie Baird C. Charles Francis Jenkins D. Philo Taylor Farnsworth 45. How many TVs were in the US in 1945? A. A few hundred C. A few million. B. A few thousand. D. A few billion.

Ở người, gen A quy định da bình thường, gen a quy định bệnh bạch tạng (các gen này nằm trên nst thường). Nếu bố mẹ đều có kiểu gen Aa thì khả năng sinh con bị bệnh bạch tạng là bao nhiêu %

Giúp mình câu h và i vs ạ. Đề bài là tìm công thức số hạng tổng quát

Tính khối lượng al2o3 có chứa số nguyên tử al gấp 4 lần số nguyên tử hidro có trong 5,6 lít hidro(đktc)

Cho đường tròn tâm O bán kính 3cm và một điểm S sao cho OS = 5cm. Từ S kẻ tiếp tuyến SA với đường tròn (O) ( A là tiếp điểm). a) Tính độ dài đoạn thẳng SA và giá trị cos của góc SOA. b)Qua A vẽ đường thẳng vuông góc với OS tại I, cắt đường tròn (O) tại B (BA). Chứng minh SB là tiếp tuyến của đường tròn (O). c) Kẻ đường kính AC của đường tròn (O). Đường thẳng SC cắt đường tròn tại điểm thứ hai là D. Chứng minh góc SID bằng góc OCD.

Cho điểm A có toạ độ (1;3) B(4;2) A) tìm toạ độ D ∈ ox sao cho : DA=DB B)tính chu vi ΔOAB C)chứng tỏ OA⊥AB . Tính diện tích OAB D) tìm toạ độ trực tâm H của ΔABC

Tứ bài thơ "Đoàn thuyền đánh cá" - Huy Cận, em hãy viết một đoạn văn 10 đến 15 dòng trình bày suy nghĩ của em về vai trò của biển đảo đối với cuộc sống con người Việt Nam.