男性,腰椎间盘术后出现深静脉血栓,其最常见的形成部位是() ["头静脉","贵要静脉","下腔静脉","髂股静脉","小腿深静脉"]
4吨/时的锅炉锅筒顶部应装()。 ["A、两只安全阀","B、一只安全阀","C、三只安全阀"]
单个细菌在固体培养基上繁殖后所形成的细菌集团() ["菌膜","菌苗","菌落","菌苔","菌体"]
下列哪个因素对毒物进入人体的机会和在体内过程有影响()。 ["个体差异","剂量、浓度和作用时间","毒物理化性质","机体的遗传性状","毒物在体内的代谢"]
35kV电力线路上安装有管型避雷器时,保护装置的动作时间不应大于()s。 ["0.08","0.1","0.2","0.3"]
说明总需求曲线为什么向右下方倾斜。