请你再说一遍。

“抱歉/对不起”（先表示歉意）；“请你再说一遍好吗？/请你重复一下好吗？”（接着询问）；“谢谢/感谢你”（最后表示感谢）。

if you can't control your manner of speaking well, then you said"你再说一遍", it might expresses that you are angry with what he just said. in normal case, we will say"什(shen)么(me)？(what?)",or "不好意思,你刚才说啥(I'm sorry,what have you just said?)", and the second answer is right too. the third one is not always used, you can say 您可以再说一遍吗or您可以重新说一遍吗or麻烦您重新说一遍好吗or麻烦您再说一遍好吗...

你能再说一遍吗？

不好意思，由于刚才您说的话语我听得不是太清楚，麻烦您可以再重新说一遍吗？谢谢