How to choose object that I add to unity3d with mouse?

Unity Engine
1

Can anyone help me to solve the problem?
I use ray to choose object with mouse, but I just can choose Terrain and can not choose the object I add to unity3d, why?
Thanks for your help.

2

does your object have a collider?

3

Yes, the object I have made a collider, and the object is a maya file, not the object that unity provides,
If I add the object that unity provides, it works well.
So I have no idea about the problem, please help me.