Hi, Lydia． Are you going to the concert on Friday- -I’d like to. But there are so manyproblems ____.

David _____ a customer when the fire started．

When I went into her room, she was _____ in her book. [ ]

Experts say ________ to sunlight for too muchtime will do harm to one’s skin.

The government will begin a series of to help the public fully understand the new educational system.