用括号内所给单词的适当形式填空。

    1. My pen pal wants me____________(buy)a ticket to the 2012 London Olympic Games.

    2.1 need to get some money__________(pay) for the new bike.

    3. Don't let the students__________(do) lots of homework.

    4. I don't want to___________(surprise) Lisa.

    5. Parents should give their children more time and___________( free) to relax.

酸牛奶中含有乳酸，其结构简式为： ，试写出：

(1)乳酸跟足量金属钠反应的化学反应方程式：____________。

(2)乳酸跟少量碳酸钠反应的化学反应方程式_____________。

(3)乳酸在浓硫酸存在下2分子相互反应生成物为环酯时，其结构简式是_____________。