The author thinks that students suffer from stress physically because they... 1. ...have heart problems. 2. ...are often too emotional. 3. ...fail to pay attention to stress signs. 4. ...come across unexpected situations.

The author thinks that students suffer from stress physically because they... 1.  ...have heart problems. 2.  ...are often too emotional. 3.  ...fail to pay attention to stress signs. 4.  ...come across unexpected situations.