The only language ____ is easy to learn is mother tongue.
–What did the old driver say ______ the bus? –He said his bus ______ an old friend and he missed it.
To make our city greener and cleaner, we need ______ trees.
–Why didn’t you answer my phone last night? –I ______ on my way home.
He is always making ______ for his being late ______ school.
______ you have nothing important to do, why not come with me to the cinema?