Câu nào sau đây là sai khi nói về sóng dừng?
A.Sóng dừng là sóng có các bụng, các nút cố định trong không gian.
B.Khoảng cách giữa hai nút hoặc hai bụng sóng liên tiếp là $ \dfrac{\lambda }{2}. $
C.Khoảng cách giữa điểm nút và điểm bụng liên tiếp là $ \dfrac{\lambda }{4}. $
D.Điều kiện để có sóng dừng là chiều của dây phải thỏa $ L=(k+1)\dfrac{\lambda }{2}. $

Trong hệ sóng dừng trên một sợi dây đàn hồi thì khoảng cách giữa hai nút liên tiếp bằng
A.nửa bước sóng.
B.một bước sóng.
C. một phần tư bước sóng.
D. hai lần bước sóng.

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
Staff members were advised that it was important ______ all projects before the end of the financial year.
A.to complete
B.completed
C.complete
D.completing

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to the following question.
The ice or a glacier that reaches the sea breaks off__________.
A.when the formation of icebergs
B.icebergs have-formed
C.and forming icebergs
D.to form icebergs

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
Half the way of the trip, we stopped _____ and let the others _____ up with us.
A.resting/to catch
B.to rest/to catch
C.resting/catch
D.to rest/catch

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to the following question.
Our teacher would like__________ .
A.us to practice our pronunciation
B.that we practicing our pronunciation
C.we to practice our pronunciation
D.us practicing our pronunciation

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
Take the time _______ these details, and call your agent if you have questions about the insurance package.
 
A.reviewing
B.review
C.reviewed
D.to review

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to the following question.
The manager regrets ____ that a lot of people will be redundant by the company next year.
 
A.to announce
B.announcing
C.having announce
D.to have announced

Choose the best answer for the following questions
I’m sorry but I didn’t mean _______you.
 
A.upsetting
B.upset
C.to upset
D.upsets

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to the following question.
Children shouldn’t be allowed ____ time ____ computer games.
 
A.to waste - playing
B.wasting – playing
C.waste - to play
D.to waste - to playing