---I’m fed up with studying.

---What nonsense! You’ve only got one year more to do. Then you’ll have your qualification and after that _____________

A．content is better than riches

B．it is not your cup of tea

C．the world is your oyster

D．well begun is half done

某太阳能热水器的水箱内装有50kg的水，太阳光照射一段时间后，水温从20℃升高到60℃．水的比热容是c_水=4.2×10³J/（kg•℃）．试求：

（1）水的温度变化△t是多少℃？

（2）水吸收的热量是多少焦耳？