[求助]大全877,283,51三道题，谢谢！

51.                             According to surveys by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine in 1979, doubling those reported in the 1977 survey.

(A) doubling those reported in the 1977 survey

(B) to double the number the 1977 survey reported

(C) twice those the 1977 survey reported

(D) twice as much as those reported in the 1977 survey


(E) twice the number reported in the 1977 survey


D为什么不对，我觉得这里用those指代前面的百分数没有错呀，因为，百分数做主语，如果后面的名词是复数，则谓语动词用复数，我就理解成在这里20 percent of young adults是复数了，对吗？


    

283.                             Even though its per capita food supply hardly increased during two decades, stringent rationing and planned distribution have allowed the People’s Republic of China to ensure nutritional levels of 2,000 calories per person per day for its population.

(A) Even though its per capita food supply hardly increased during

(B) Even though its per capita food supply has hardly increased in

(C) Despite its per capita food supply hardly increasing over

(D) Despite there being hardly any increase in its per capita food supply during

(E) Although there is hardly any increase in per capita food supply for

Even though its per capital....，这里的its指代明确吗，我总觉得它应该指代后面的Peoele's Republic of China，这样的话，B选项就不对了，请帮我解释一下。

877.                             Traveling the back roads of Hungary, in 1905 Béla Bartók and Zoltán Kodály began their pioneering work in ethnomusicology, and they were armed only with an Edison phonograph and insatiable curiosity.

(A) Traveling the back roads of Hungary, in 1905 Béla Bartók and Zoltán Kodály began their pioneering work in ethnomusicology, and they were armed only

(B) In 1905, Béla Bartók and Zoltán Kodály, traveling the back roads of Hungary, began their pioneering work in ethnomusicology, and they were only armed

(C) In 1905 Béla Bartók and Zoltán Kodály began their pioneering work in ethnomusicology, traveling the back roads of Hungary armed only

(D) Having traveled the back roads of Hungary, in 1905 Béla Bartók and Zoltán Kodály began their pioneering work in ethnomusicology; they were only armed

(E) Béla Bartók and Zoltán Kodály, in 1905 began their pioneering work in ethnomusicology, traveling the back roads of Hungary, arming themselves only

C选项中的armed only前面是不是应该有逗号，不然，它前面有名词Hungary，总觉得armed only修饰谁有歧义，而且，A选项就是绝对错的吗，还是说不如C好。

    


谢谢！