学习目标：
New words:UFO,barber,bathroom, alien,kitchen,bought, land, got, while
Key phrases: get out, take off
Key sentences:
⑴.—What were you doing when the UFO arrived?—I was cooking dinner in the kitchen.
⑵—What was he doing when the UFO arrived?—He was sleeping late when it arrived.
⑶The girl was shopping when the alien got out.
⑷While the girl was shopping, the alien got out.
学习重难点：◆重点 掌握过去进行时态的用法。◆难点掌握when和while的用法。
