Here we are at the science museum. Let’s _______.
—What’s your favorite ________?—Summer. Because I can swim in rivers.
David usually takes _______ walk for an hour after dinner.
The population of the world still now.
— Excuse me. Is the library open all day?— . Only from 8 a.m. to 4 p.m..
Keep off the drugs(毒品), you and your family will be in great danger?