美式看跌期权和欧式看跌期权的权利金不应该高于执行价格。（）

下面是学校为保护学生视力做出的要求。请根据以下要点写一封信告诉你的朋友Jack怎样保护视力。要点：1. Hold a book at least 30 cm away from the students’ eyes while reading.

2. Place the computer at least 50 cm from the students.

3. Look out of the window at objects that are far away.

4. Check the students’ eyes regularly by a doctor.

5. Do eye exercises both at school and at home.

要求: 可适当增加细节。词数100字左右。

Dear Jack,

How are you getting on with your studies? I’m sorry that you have got the eyesight problems. ____________________________________________________________________________________________________________________________________________________________________

Yours truly