---Can you tell me _______?

---With Lucy’s help.

A．when you did it so well

B．when did you do it so well

C．how you did it so well

D．how did you do it so well

椎间盘（）

A.位于脊柱各椎骨之间

B.由纤维环、髓核和透明软骨组成

C.纤维环由多层透明软骨构成

D.透明软骨围绕于椎间盘的最外层

E.成人总数为25个