What is the exact meaning of ageism?
A.A negative period of impotency and incompetency.
B.A negative and/or stereotypical perception of older adults.
C.A definition of stereotypical and often negative attitudes.
D.A denotation against the negative bias of older adults.
第3题
钎焊时,冷阱安装在()。
A.扩散泵与真空阀之间
B.机械泵与真空阀之间
C.增压泵与真空阀之间
第4题
钎焊真空炉选用两级抽气来获得所需的真空度时,采用的方式是()。
A.机械泵+增压泵
B.机械泵+扩散泵
C.增压泵+扩散泵
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