—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
I tried to come closer to watch the bird, but as soon as it noticed me, ____ into the woods.
She _______ his number in the phone book to make sure that she had got it right.
Teachers have to constantly update their knowledge in order to maintain their professional __________.
I don’t like fish, so I ________ eat it unless I was extremely hungry.
I have no idea ____________ measures the government will take to stop the river from being further polluted.