—What seems to be the problem?

—____

—How long have you been like this?

—Since Saturday night.

—____ 

—Yes, I also feel lighthearted.

—Can you think of anything you ate Saturday that might have caused it?

—All I can think of is the fish I had. It didn't taste quite right.

—____  Now I'll give you some medicine. Take it and you should be feeling better soon.

—____

—I also suggest that you follow a special diet.

—____ 
—You should stick to eating lighter foods.

A:What's that?

B:That might be it.

C:Thank you, doctor.

D:Any other problems?

E:I have a running nose.

F:Have you seen a doctor?

G:I have a terrible stomachache.

____是主要的遗传物质．

读黄河干流泥沙沿途的变化示意图，回答下面小题．