_____ the government recovers the vehicle purchase tax and the oil prices go up continuously, the sales of the vehicle in China are still increasing every year.

A．When

B．Once

C．Since

D．While

质地最硬的肿瘤是（）

A.纤维瘤

B.平滑肌瘤

C.骨瘤

D.脂肪瘤

E.腺瘤