Linda's answers are good. However, No. 2 could be improved as follow: a. I would like to play, but I have yet to finish my homework, or b. I would like to play, yet I have to finish my homework.

1. I haven't finished my homwork yet. 这里 yet 的解释是"还没有".你只要记得,在否定句和疑问句里,你想用 already 的地方,都应该用 yet 来代替. 2. I would like to play, yet I haven't finished my homwork. 这里的 yet 意思是"但是",和 but 一样用法,但比较口语化.