A: Hi, Tom. You were not here yesterday afternoon. What was wrong?

B:                                    ( 1)  .

A: Sorry to hear that.  __________________________( 2)?

B: Much better. The fever is gone. But I still cough and I feel week.

A:                                     ( 3)?

B: Yes, I did . I went to the doctor’s yesterday afternoon. The doctor gave me some medicine and asked me to stay in bed for a few days.

A:                                       （4）       ?

B: Because I’m afraid I’ll miss more lessons and I will be left behind.

A:Don’tworry.Take good care of yourself.                                          ( 5) .

B: Thank you.

DEH系统的主要功能有哪些？