Her mother is ill and she is looking _____ her at home.[ ]
A. after
B. at
C. about
答案:A
调幅波的解调器是(),调频波的解调器是()。
色甘酸二钠主要用于()
A.改善通气功能
B.预防哮喘发作
C.哮喘重症发作
D.抗感染
E.镇咳祛痰