【题目】As some of these actors could not sing well enough, they had to ________ other musicians to help them.
A.rely on
B.work on
C.focus on
D.go on

【答案】A
【解析】rely on意为“依赖，依靠”；work on意为“致力于”；focus on意为“集中(注意力、精力)于”；go on意为“继续”。句意：由于这些演员唱得不足够好，他们只好依赖别的音乐家来帮助他们。故选A。