风痰的特征是
A．色黄粘稠B．白而清稀C．清稀多泡沫D．白滑而量多E．少而粘稠
参考答案：C
若不等式ax+（2a-1）y+1＜0表示直线ax+（2a-1）y+1=0的下方区域，则实数a的取值范围为______．
— Did you arrive here this morning?
— Yes, it was at nine o'clock _____ we came here. [ ]
A. when
B. before
C. which
D. that
