请教2条白勇语法题

19 Researchers have questioned the use of costly and experimental diagnostic tests to identify food allergies, such as milk, that supposedly disrupt normal behavior.
(A) to identify food allergies, such as
(B) to identify food allergies, like
(C) to identify food allergies, such as to
(D) for identifying food allergies, like that of
(E) for identifying food allergies, such as for

答案C，请问为什么要加to呢？

26 In its most recent approach, the comet Crommelin passed the Earth at about the same distance and in about the same position, some 25 degrees above the horizon, that Halley's comet will pass the next time it appears.
(A) that Halley's comet will pass
(B) that Halley's comet is to be passing
(C) as Halley's comet
(D) as will Halley's comet
(E) as Halley's comet will do

答案D, 需要倒装，又因为是the next time，所以用will, 这么理解对吗？