答案是 D.如果你能答应不用我的电脑,我就可以让你呆在我家里.
provided 是连词,也可可以说provided that.意思是“如果……的话”“只要”又如：
They may swim provided an adult accdompanies them.
She may come with us provided (that) she arrives in time.
不可以选C,如果选C,则前面应为否定句,意思才成立,因为unless是“如果不”等于if not.如果选unless,前面则要用否定式,You can't stay in my room__unless___you promise not to use the computer.如果你不答应不使用我的电脑,我就不让你呆在我的家里.这样意思才能讲得通.