[求助]PREP破解中并列结构疑问？THX

~好心人帮我看看吧~

45.The application of a new method for analyzing the chemistry of tooth enamel allows scientists to
examine molars of prehuman ancestors and determining that their diets were more varied than had
been supposed.

(A) The application of a new method for analyzing the chemistry of tooth enamel allows scientists to
examine molars of prehuman ancestors and determining
(B) Through the application of a new method for analyzing the chemistry of tooth enamel, the
molars of prehuman ancestors were examined by scientists who determined

(C) When they applied a new method for analyzing the chemistry of tooth enamel, scientists
examined molars of prehuman ancestors, determining
(D) Applying a new method for analyzing the chemistry of tooth enamel, the molars of prehuman
ancestors have been examined by scientists, who determined
(E) Applying a new method for analyzing the chemistry of tooth enamel, scientists have examined
molars of prehuman ancestors and determined

(E)  正确;have examined…and determined…结构平行

77.Scientists have found signs that moving water changed the chemical makeup of the surface of Mars
in recent eras, therefore concluding that its crust is harboring up to three times as much water than
was previously thought.

(A) eras, therefore concluding that its crust is harboring up to three times as much water than was
(B) eras, therefore concluding that the planet's crust harbors up to three times as much water or
more as was
(C) eras and have therefore concluded that the planet's crust harbors up to three times as much
water as
(D) eras and they have concluded, therefore, that its crust harbors up to three times as much water,
or more, than
(E) eras and concluded, therefore, that the planet's crust is harboring up to three times more water
as was

(C)  正确，Scientists have found…and have therefore concluded结构平行

(E)  没有时间证据,concluded应该改为现在完成时,跟前一个并列成分使用同一个时态

77题：句子结构: Scientists have found…and have therefore concluded that…
 

45题：句子结构: Applying…, scientists have examined …and determined that…
 

同样是正确答案，为什么感觉是矛盾的呢？若45对了，那77就应该选D吖？

“sb. have V-ed... and have V-ed”中第二个have到底可不可以省呢？