Look and answer.

1. A: What did he do last weekend?

    B:                               .

2. A: What are they going to do?

     B:                               

3. A: What's the matter, Helen?

    B:                                .

4. A: What did she do yesterday evening? 

    B:                                .

目前有关脂蛋白受体的研究并不深入的是 （）

A.LDL受体

B.VLDL受体

C.HDL受体

D.清道夫受体

E.ApoE受体