皱纸状白斑多见于（）。
A.唇红黏膜
B.口角区颊黏膜
C.舌腹口底黏膜
D.牙龈黏膜
E.软腭黏膜
参考答案：C
函数y＝ax－3＋3恒过定点________．
Don't worry. They'll come to help us _______.[ ]
A. in half an hour
B. in a half hour
C. after half an hour
D. after a half hour
