From the passage, it can be inferred that the experimental polio vaccine was given to people by____________.

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

My mother has____________for a bargain.

The (A) better you (B) are at English, (C) more chance you have to get (D) a job with international organizations.

Such a doctor____________retire from his job before the retirement age.

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

(A) It's thirty years (B) since this (C) fifty-storeys building (D) was built.

How well people remember things____________on many different factors,

My wife was good enough to____________my mistake.

Never in my life____________such an intelligent boy.