--It is really fun to hike and I often go hiking in the forest.--But hiking alone in the forest ______ be very dangerous.

You’d better take another flight to New York , for the AA 505 Flight ______ have been cancelled. But you should call the airport to make sure. 

 — The socks must be Linda’s.— No, they         be. They’re too small for her.

—The government should try to balance economic growth and pollution from industry.—____. It’s time to do it.

—Whose workbook is this, Tony?—Look! Ann's name is on it! It ______ be hers.