all of them are strong candidates only one will be chosen for the post.A. SinceB. IfC. A

问题补充：

all of them are strong candidates, only one will be chosen for the post.

A. Since

B. If

C. As

D. While

答案：

A. Since

B. If

C. As

(答案→)D. While

解析：句意：尽管他们都是强有力的候选人，但是仅仅有一个将被选上担任这个职务。since既然；if如果；as 因为；while尽管，根据句意故选D。