I have good reason to be suspicious.
我的怀疑有充分理由。
There is no reason to disbelieve him.
没理由不相信他。
Are you angry with me for some reason?
你是因为某个原因生我的气了吗？
This was the real reason for her call.
这是她打电话的真实原因。
He said no but he didn't give a reason.
他说不行，但没有说明原因。
There seems no reason to doubt her story.
似乎没有理由怀疑她所说的话。