请教几道大全

25.   One reason why more young people lose their virginity during the summer than at other times of the year undoubtedly is because school vacations give adolescents more free time.

(A) One reason why more young people lose their virginity during the summer than at other times of the year undoubtedly is because

(B) If young people lose their virginity more during the summer than other seasons, it is undoubtedly because

(C) One undoubtable reason that young people lose their virginity more during the summer than other times is

(D) One reason more young people lose their virginity during the summer than at other times of the year is undoubtedly that（D）

(E) Young people lose their virginity more often during the summer undoubtedly because, for one reason,

为啥选D     one reason 后面难道可以省略同位语that 吗

6.     As a baby emerges from the darkness of the womb with a rudimentary sense of vision, it would be rated about 20/500, or legally blind if it were an adult with such vision.

(A) As a baby emerges from the darkness of the womb with a rudimentary sense of vision, it would be rated about 20/500, or legally blind if it were an adult with such vision.

(B) A baby emerges from the darkness of the womb with a rudimentary sense of vision that would be rated about 20/500, or legally blind as an adult.

(C) As a baby emerges from the darkness of the womb, its rudimentary sense of vision would be rated about 20/500; qualifying it to be legally blind if an adult.

(D) A baby emerges from the darkness of the womb with a rudimentary sense of vision that would be rated about 20/500; an adult with such vision would be deemed legally blind.（D）

(E) As a baby emerges from the darkness of the womb, its rudimentary sense of vision, which would be deemed legally blind for an adult, would be rated about 20/500.

为什么选D？

17.   The Gorton-Dodd bill requires that a bank disclose to their customers how long they will delay access to funds from deposited checks.(P4 F-5)

(A) that a bank disclose to their customers how long they will delay access to funds from deposited checks

(B) a bank to disclose to their customers how long they will delay access to funds from deposited check

(C) that a bank disclose to its customers how long it will delay access to funds from deposited checks

(D) a bank that it should disclose to its customers how long it will delay access to funds from a deposited check（C）

(E) that banks disclose to customers how long access to funds from their deposited check is to be delayed

为什么是c  觉得E 也没错啊
                摸不清该题的考点是什么  请多指教

23.   Tiny quantities of more than thirty rare gases, most of them industrial by-products, threaten to warm the Earth’s atmosphere even more rapidly than carbon dioxide during the next fifty years.

(A) to warm the Earth’s atmosphere even more rapidly than carbon dioxide during the next fifty years

(B) to warm the Earth’s atmosphere even more rapidly over the next fifty years than carbon dioxide will比较的前半句为什么不用将来时？

(C) during the next fifty years to warm the Earth’s atmosphere even more rapidly than carbon dioxide

(D) a warming of the Earth’s atmosphere during the next fifty years even more rapid than carbon dioxide’s（B）

(E) a warming of the Earth’s atmosphere even more rapid than carbon dioxide’s will be over the next fifty years