--Your effort is sure to pay __________ ---Thank you for your encouragement.
The number of people in the world ______ about 6 billion and large quantities of waste ________ each year.
You should have told me there was no meeting today, I ___ have run all the way here through the heavy rain.
Always read the ________ on the bottle carefully and take the right amount of medicine.
– What do you think of teaching, Bob?-- I find it fun and challenging. It is a job ________ you are doing something serious but interesting.
America is an ________ country.