骨质增生由下述哪种原因引起()

A．骨动脉或静脉栓塞及血栓形成

B．肿瘤组织形成的肿瘤骨

C．成骨细胞活动形成新生骨或软骨内成骨

D．软骨细胞活动形成新生骨

E．以上都不是

—We don’t permit____ in our school. Would you please put your cigarette out?

—Forgive me. I didn’t know.

A．to smoking

B．to smoke

C．smoking

D．having smoked