It is widely accepted that young babies learn to do things because certain acts lead to________.

What is your best friend like — .

Who’s the man over there Is it Mr. Black— It _________ be him. He’s much taller.

She told me that she had mailed part of the products and that the rest ______ in a few days.

If eating makes you feel better, you can go to your favourite restaurant to have a nice meal. The sentence elements(成分) of the underlined parts is_______.