瓜蒌的适应证是（）
A.痰热喘咳
B.胸痹、结胸
C.肺痈、肠痈、乳痈
D.肠燥便秘
E.食积、脘腹胀痛
参考答案：A, B, C, D
若x2-y2=48，x+y=6，则3x-3y=______．
The headmaster stopped _____ to me because there was a call for him.[ ]
A. talking
B. to talk
C. saying
D. to say
