26. This is the house that Jack ______ three years ago. A. was building B. builds C. had built D. built 27. He ___________ the effects of radiation when he suddenly died A. was studying B. studied C. had been studying D. has studied 28. The train ______ when I ______ at the station. A. already left / had arrived B. already had left / arrived C. left already / had arrived D. had already left / arrived 29. Everyone was asleep when the enemy _____________ A. had attacked B. attacked C. was attacking D. attacking 30. Don't make noise. My mother ________________with her friends. A. talked B. talks C. is talking D. was talking 31. She ______ the piano since she ______ ten years old. A. played / was B. has played / has been C. has played / was D. had played / was 32. Up to now, I _________________ a lot of information about her. A. learnt B. would learn C. learn D. have learnt 33. Mary ___________ in London for 15 years. A. lives B. was living C. is living D. has lived 34. We were disappointed that most guests ___________ when we arrived at the party. A. had left B. has left C. left D. leave 35. He never goes home before he ______ his work. A. finished B. has finished C. had finished D. finishing 36. Before cars ______, people ______ horses and bicycles. A. were discovered / had used B. has been discovered / have been using C. is discovered / using D. discovering / used 37. I ______ my writing by 3 o'clock this afternoon. A. will finish B. finish C. will have finished D. finished 38. How ______ since we ______ school? A. will you / left B. are you / left C. have you been / had left D. have you been / left 39. When I last ___________ Jane, she ____________ to find a job. A. have seen/ tried B. saw/ tried C. see/ is trying D. saw/ was trying 40. Next week when there ______ a full moon, the ocean tides will be higher. A. is B. will be C. is being D. will have been 41. I sat near a window whenever I ______ a bus. A. have taken B. had took C. took D. take 42. When I last saw him, he _________in London. A. is living B. was living C. has lived D. has been living 43. We ________________Mary since last Saturday. A. don't see B. hadn't seen C. didn't see D. haven't seen 44. The train __________________haft an hour ago. A. has left B. had left C. left D. has been leaving 45. By Christmas, I ________________for Mr. Smith for six years. A. shall have been working B. shall be working C. shall work D. have been working 46. I'll come and see you before I ____________for HCM City. A. will leave B. shall leave C. have left D. leave 47. Jack ___________ the door. A. has just opened B. opening C. open D. will have opened 48. By the age of 25, he ________________two famous novels. A. had written B. has written C. writes D. wrote 49. After I ____________lunch, I looked for my bag. A. have had B. had had C. had D. was having 50. The man got out of the car, ______round to the back and opened the door. A. walk B. walking C. walks D. walked 51. Before you asked, the letter ________________. A. has been written B. was written C. had been written D. had written 52. I ______________in Hanoi before I moved to HCM City. A. had been living B. had lived C. have lived D. have been living

Cho đường tròn ( o ,r) Và điểm m cố định nằm ngoài ( o ,r) Từ m kẻ các tiếp tuyến MA ,MB

tìm các số nguyên x y biết 5xy-5x+y=5

1, vào ngày tháng năm nào nước ta tưởng nhớ hai bà trưng? 2,nhà hán đặt bộ máy quan lại đối với Âu Lạc đến tận cấp nào? 3,từ thế kỉ 7 đến thế kỉ 9 có các cuộc khỏi nghĩa đã nổ ra đó là cuộc khởi nghỉa nào?

Câu 16 : Tính 4x^2 + 3x^2y^3 + ( -5x^2y^3 ) là

Giúp mình pthh với ạ : $1. RCHO + H_2 ⇄$ $2. CH_3COOH + Na \to$ $3.HCOOH + KOH \to$ $4. CH_3COOH + C_2H_5OH ⇄$ $5. RCOOH+ ROH ⇄$ $6. RCHO + AgNO_3 + NH_3 \to$

MỌi người giúp mình với ạ Mình cần gấp ạ cảm ơn ạ

cho mình xin đáp án câu này với

Cho tam giác ABC có diện tích 516dm2 .Trên cạnh BC lấy hai điểm P,Q sao cho BP=PQ=QC.Từ P kẻ đường thẳng song song với AC.từ Q kẻ đường thẳng song song với AB,hai đường thẳng này cắt nhau tại M. a)So sánh SAMC VÀ SAPC b)Tính SAMC

Cùng một lúc ô tô đi từ A đến B với vận tốc 55 km/giờ và xe máy đi từ B về A với vận tốc 47km/giờ. Quãng đường AB dài 225km. Hỏi mấy giờ hai xe khởi hành (biết hai xe gặp nhau lúc 1 giờ chiều)