He had to retire(退休)early poor health.A. as a resultB. becauseC. soD. because of

问题补充：

He had to retire(退休)early poor health.

A. as a result

B. because

C. so

D. because of

答案：

A. as a result

B. because

C. so

(答案→)D. because of

解析：as a result因此，结果是； because因为，接从句；so因此；because of因为，接名词性短语。句意：因为身体不适，他不得不提前退休。结合语境可知选D。