当婆媳吵架，作为儿子和丈夫的男子夹在其中不知所措，这属于（）.
A.角色学习
B.角色期待
C.角色认知
D.角色冲突
参考答案：D
According to the passage, ______.
A．all people can take beta blockers
B．beta blockers are widely prescribed
C．beta blockers work only on test anxiety
D．beta blockers work only to improve test scores if the test-taker truly knows the material
简述供应商选择以及采购数量确定的方法
