D. conscious

正确答案：D

51. Clark felt that his _____ in one of the most dramatic medical experiments of all time was

worth the suffering he underwent.

A. appreciation

B. participation

C. presentation

D. apprehension

正确答案：B

52. By _______computation, he estimated that the repairs on the house would cost him a

thousand dollars.

A. coarse

B. rude

C. rough

D. crude

正确答案：C

53. A ___ woman wouldn't weep just because her husband had forgotten her birthday.

A. reasonable

B. rational

C. unreasonable

D. irrational

正确答案：B

54. Agriculture was a step in human progress _______ which subsequently there was not

anything comparable until our own machine age.

A. in

B. for

C. to

D. from

正确答案：C

55. In Britain people _____________ four million tons of potatoes every year.

A. consume

B. dispose

C. swallow

D. exhaust

正确答案：A

56. He picked up a stick to ____ him _____ the dog.

A. defend, with

B. defend, from

C. pretend, from

D. defend, for

正确答案：B

57. I suffered from mental ______ because of stress from my job.

A. release

B. relief