— I feel ______ a pity that I didn't attend Professor Smith's lecture.

— You really should have.[ ]

A. this

B. it

C. that

D. one

下列脑肿瘤中，哪种“囊变率最低”()

A．血管母细胞瘤

B．胶质瘤

C．颅咽管瘤

D．脑转移瘤

E．脑膜瘤