—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
We elected him _____ headmaster of the school for _____ second time.
--What does Tom study? --He studies _____ science of _____ sound.
It’s _____ pleasure to see _____ sun rising in _____ east.
One piece of work of _____ United Nations is to help _____ poor in _____ developing countries.
Tom stands up for _____ oppressed.