The students asked _________________.

A．when can they surf the Internet in class

B．when could they surf the Internet in class

C．when they could surf the Internet in class

D．when they can surf the Internet in class

关于甲状腺的结构的描述中，哪一项错误？（）

A.腺细胞围成滤泡状结构

B.胞质内有丰富的滑面内质网和脂滴

C.滤泡腔内充满胶状物

D.滤泡上皮的高低与机能状态相关