ps 发光字:After I sent the letter asking for a job, I had nothing to do but await the answer.

After I sent the letter asking for a job, I had nothing to do but awaiting (waiting) the answer.
but 是介词,不能直接加动词.

你的原句中用的是 await 啊
后来的补充里又问的是wait 我不太理解啊
这里的应该用动词 所以只是wait
而not to do but do是对的啊
所以只用wait就没问题了

After I had sent the letter asking for a job, I had nothing to do but await the answer.

可以，只是觉得await过于正规了一点点，用wait for 就可以了。ask for 改为 apply for也好一些。当然还有上楼说的reply一词。

After I sent the letter asking for a job, I had nothing to do but wait for the answer/reply.

After I sent the letter applying for a job, I had nothing to do but waiting for the reply.

After I sent the letter applying for a job, I did not have much to do but wait for the reply.

After I sent the letter asking for a job，这典型的中式英语。。。。答复也不能用answer（这是回答问题，你又没问招聘单位问题）

这个：After sending the resume,i had nothing to do but wait for the reply.
very good