Directions : There are 15 incomplete sentences in this section. For each sentence there are four choices marked A, B, C and D. Choose one answer that best completes the sentence and blacken the corresponding letter on the Answer Sheet. 6. Jonathan and Joe left the house to go for__ after supper.
A、walk
B、the walk
C、wallks
D、a walk
51. What does the author say about the assumptions made about the intentions behind a person's behavior?
A、They should be trusted.
B、They are often bold.
C、They are often incorrect.
D、They should be encouraged.
52. What does the underlined word "centenarians" in Paragraph 1 refer to?