Have you ever traveled abroad?–SureI ____ the language of English in the USA two years after I graduated from the university

Now the air in Yancheng is _______ than it used to be . We should do something to stop it .

Mom, shall we go hiking tomorrow—Oh, dear. That depends on it is fine tomorrow.

He reminded me of what I should ________ have forgotten[ ]

With the help of the Internet, we can get all kinds of information we need.[ ]