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

问题补充：

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

A. Since

B. As

C. If

D. While

答案：

A. Since

B. As

C. If

(答案→)D. While

解析：连词辨析。A. Since“既然”表原因 B. As “因为、当…时候、虽然”作虽然讲时要用倒装语序 C. If 如果 D. While 虽然虽然他们都是强有力的竞争者但是这个岗位只选一个人。根据句意选D