人类能听到的声音频率x不低于20Hz,不高于2000Hz,用不等式表示为( )Hz。
20≤x≤2 000
21.Have you heard_____report? People with______good knowledge of engineering are in great need in the job market.
A.a; a
B.the; a
C.a; /
D.the;/
关于固定型药疹描述不正确的是:()
A.皮疹愈合后留下灰黑色色素斑,约一周消退
B.皮疹好发于皮肤黏膜交界处
C.典型皮疹为圆形或类圆形的水肿性暗紫红色斑疹
D.皮疹常为一个
E.黏膜皱褶处糜烂时常感疼痛