Mark the letter A, B, C, or D to indicate the underlined part that needs correction in each of the following questions.

Most oxygen atoms have eight neutrons, but a small amount have nine or ten.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Quan Ho singing is a Vietnamese style of folk music _____ by UNESCO in 2009.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Don't waste time _____ for a cheap hotel when you arrive. They are all about the same price.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions. 

She got terrible marks in the mid-term tests. She _____ harder for them.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Some security measures have been _____ to prevent the infection of Corona virus.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Many women find it hard to _____ both a job and a family.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Nam passed the exam easily _____ it was very difficult.