I breaked down his PSP just now,so he must be crying now

这句话是正确的.
当中可以用and连接也可以,但如果是选择题的话就乖乖选so好了.
直接加个逗号是不行的.

对的，用and也可以。
但是直接加逗号不行，因为逗号不能直接连接两个句子，而“I breaked down his PSP just now”和“ he must be crying now”都可以构成一个单独的句子。

I have broken down his psp just now, so he must be crying now.

正确