My English teacher gave us a suggestion yesterday, _____is often the case, ______ our monitor organize a debate after class.

A．which, which

B．which, that

C．as, that

D．as, which

下述“尤文肉瘤”的知识，哪项正确

A．成年人多见

B．常有骨、肺转移

C．常有特征性骨膜反应

D．好发于长骨干骺端

E．髓腔内多有成骨性改变