皮皮学，免费搜题
登录
搜题
【单选题】
以下关于灭火器的使用方法不正确的是（）。A.
泡沫灭火器喷射泡沫时，泡沫直射液面灭火
B.
使用二氧化碳灭火器使喷筒从火源侧上方喷射
C.
在室外使用干粉灭火器，应该选择在上风方向喷射
D.
使用清水灭火器时要刺穿瓶口之密封膜片
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【多选题】使用索氏提取器进行固液提取,下列观点正确的有:
A.
利用了溶剂回流及虹吸原理，固体物质反复被纯溶剂浸润、萃取，效率较高
B.
无需拆解装置，相当于多次回流连续进行，方便快捷
C.
浸润的固体必需用滤纸等包裹起来，避免细小固体颗粒浮出，堵塞虹吸管
D.
滤纸筒中的固体不要高过虹吸管，否则萃取效果不理想
【单选题】Economists normally assume that the goal of a firm is to:
A.
sell as many units of output as possible.
B.
maximize profits.
C.
sell products at the highest prices possible.
D.
maximize sales revenue.
【单选题】Economists normally
A.
do not try to explain people's tastes, but they do try to explain what happens when tastes change.
B.
believe that they must be able to explain people's tastes in order to explain what happens when tastes change.
C.
do not believe that people's tastes determine demand, so they ignore the subject of tastes.
D.
incorporate tastes into economic models only to the extent that tastes determine whether pairs of goods are substitutes or complements.
【单选题】Economists normally assume that the goal of a firm is to
A.
maximize its total revenue.
B.
maximize its profit.
C.
minimize its explicit costs.
D.
minimize its total cost.
【单选题】Cheer up! Never let your failures _____ trying harder.
A.
put you through
B.
put you off
C.
put you across
D.
put you away
相关题目：