怎么解释诚信通:what is that?

what is that? that that that that that man said is what you want He is certais that dictionary is just what I want He is certais that dictionary is just what I want He is certais that dictionary is just what I want He is certais that dictionary is just what I want Believe that doing what is right is important This is( )I need. a.that b.what What is that we never borrow but often return? What is that we never borrow but often reture?