咬肌的起始部位为
A．颞窝
B．翼外板内侧
C．腭骨锥突
D．蝶骨大翼
E．上颌骨颧突及颧弓下缘的前2/3和 颧弓深面
参考答案：E
已知M={1}，N={1，2}，设A={（x，y）|x∈M，y∈N}，B={（x，y）|x∈N，y∈M}，则A∩B=______，
A∪B=______．
It is selfish _____ him _____ the people in trouble. [ ]
A. for, to help
B. for; not help
C. of; to help
D. of; not to help
