在催化剂作用下，乙酸可通过两步反应得乙烷，反应原理如下： ①_爱下问搜题

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问题不定项选择题

在催化剂作用下，乙酸可通过两步反应得乙烷，反应原理如下：

①CH₃COOH+2H₂→CH₃CH₂OH+H₂O

②CH₃CH₂OH+H₂→CH₃CH₃+H₂O

③CH₃COOH+3H₂→CH3CH₃+2H₂O

在反应过程中乙酸和乙醇会生成乙酸乙酯。分别考查加Mo(钼) 和不加Mo负载型Ni(镍)催化剂催化效能，某文献记载的数据如下：下列叙述不正确的是

[ ]

A．上述①②③三反应均属于加成反应

B．上述①②③三反应中有机物均发生还原反应

C．乙酸加氢脱氧反应260℃比240℃进行更有利

D．Mo₁₆ Ni₆催化性能比Ni₆好

答案

答案：A

完形填空

A high school history teacher once told us, “If you make one close friend in school, you will be most fortunate. A true friend is someone who stays with you for life."_26_ teaches that he was right. Good friendship is just not easily _27_.
It is possible that we simply do not stay in one place long enough for_28_friendship to _29_. However, there can be_30_disagreement on the need for each of us to think carefully about the kind of friendship we want.
To most of us, friendships are considered very important, but we need to have it clear in our _31_ what kinds of friendship we want. Are they to be close or _32_ at arm's length? Do we want to _33_ourselves or do we want to walk on the surface? For some people, many friendships on the surface are _34_enough—and that' s all right. But at some point we need to 35 that our expectations are the same as our friends' expectations. The sharing of_36_experience _37_ our tears as well as our dark dreams is the surest way to deepen friendships. But it _38_be undertaken(进行) slowly and carried on only if there are _39_of interest and action in return.
　　What are some of the _40_of friendship? The greatest is the attraction to expect too much too soon. Deep relationships _41_time. Another “major difficulty" is the selfishness to think one “possesses" the other, including his time and attention. Similarly, friendships _42_ actions in return. In 43 words, you must give as much as you take. Finally there is a question of taking care of. Unless you spend _44_time together, talking on the phone, writing letters, doing things together, friendships will die _45_.

A．difficulties

B．differences

B．comfortable

单项选择题

诊断轴承、齿轮、回转机械是否异常的技术方法是测其运动时是否有（）。

A、润滑油

B、响声

C、异常振动