"Be up to" 和 "Be up for"的用法和区别：
1. What are you up to? = What are you doing?
2. You're up to it. = You are good enough ( to do it )
3. It's up to you. = It depends on you.
4. I'm up for that. = I want to do that.
......更多表达和详细解析请看视频~ http://t.cn/RpuwUfs ​