以下哪征象有助于鉴别髓母细胞瘤和室管膜瘤（）
A.密度稍高
B.均一增强
C.脑积水程度
D.沿脑脊液播散种植转移
E.第四脑室形态
参考答案：E
—I am really struck by your spoken English. You speak so fluently. Have you been abroad.
—Yes, I ________ in London for two years．
A．have stayed
B．stayed
C．had stayed
D．have been staying
