Public service advertisements are often run _____ free, and are ______ to educate people about health, safety, or any other issue which affects public welfare.
---You should have thanked her before you left. ---I meant _______. But when I was leaving I couldn’t find her anywhere.
.Hawking became world-famous in _______.
It is thought that one billion people I the world, _____is half the word’s workers, earn their living by farming.
I think whoever makes____contributions to the company than the others should get____income.
Our teacher is always busy preparing lessons until 11 o’clock at night, _____we students have gone to sleep.