下列是由局部刺激因素引起的牙周疾病，但不包括
A．成年人牙周炎
B．龈 * * 炎
C．多发性龈脓肿
D．单纯性龈炎
E．肥大性龈炎
参考答案：C
集合P={-1，1}，Q={0，1，2}，则P∩Q=______．
—I didn't go to class last night because my car broke down.
—You mine. I wasn't using it.[ ]
A. should borrow
B. might have borrowed
C. could have borrowed
D. must have borrowed
