There are some police cars in front. What do you suppose _____?

My train arrive in New York at eight o'clock tonight. The plane I would like to take from there ______by then.

Thegreatuseofschooleducationisnotsomuchtoteachyouthings_____toteachyoutheartoflearning.

Modern science and technology has _____ communication between people far apart.

This robot is supposed to save a lot of labor, but it remains a problem if it ______.