1. What do you think of the new _______（制度）？
2. “What happened？” John’s mother asked him in a _______（温和的） voice.
3. Before the Earth’s protective ________（大气层） was formed，there was no life except in the sea.
4. With the____（引力） of the moon and the sun each day，thus （潮汐） roll in and roll away.
5. He managed to finish the race, ______（不像） more than half of the competitors.
