An advertisement is useful in ________ it lets customers know of the kinds of goods in the shops.

The students wonder____good the course will do to their future jobs.

Doctors have been researching 　　　　 effect stand-up and other forms of comedy have on us.

---We can use QQ to talk with each other on the Internet.---Really? But can you tell me _______it.

Many young people in the West are expected to leave ______________ could be life’s most important decision — marriage — almost entirely up to luck.