计算题：试计算直径φ8mm拉伸试样的标距？

Tracert功能是（）.

A、用于检查网管工作是否正常

B、用于检查网络连接是否可通

C、用于分析网络在哪里出现了问题

阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空。

Last year, my brother and I went to Miami for a vacation. Some of my friends who had been there before said_小题1:_____ was a wonderful holiday destination. Before we went, we had planned for months. When the day came, we were ready.

After our plane landed, we went to the hotel. We had made our reservation six months__小题2:____ （early）, but the man at the front desk said there had been a mistake. We 小题3:_____（tell）that our rooms hadn’t been reserved for that week, 小题4:_____ for the week after. I didn’t understand 小题5:____ this would happen and my credit card had already been charged小题6:______ the reservation. What’s worse, the hotel had been fully booked. When we were wondering what to do, the manager came out. She was 小题7:_____（surprise）helpful. She apologized for the mistake and gave us a spare VIP room on 小题8:_____ top floor. We had never stayed in such an amazing room, and we weren’t charged extra.

The next day, my brother and I went to the beach 小题9:____ we watched some people play volleyball. We got a little小题10:_____（sunburn），but the day had been so relaxing that we didn’t mind.

I want to know _____ .

A．when will he come back

B．when he will come back

C．when he comes back

D．when is he coming back

In theory, the Habbendorf rotary engine could be a great racing engine, but in practice, it is not. The reason is that the available fuels do not have sufficient octane to obtain maximum performance from the engine.
The answer to which of the following questions would be most relevant to evaluating the adequacy of the explanation given above for why the Habbendorf rotary engine is not a great racing engine ？（）

A. If the Habbendorf rotary engine were to operate at maximum performance levels, how would its performance compare to that of an engine recognized as a great racing engine

B. At what level of octane in its fuel does the Habbendorf rotary engine achieve maximum performance

C. What levels of speed, acceleration, and efficiency must an engine display in order to be considered a "great racing engine"

D. Could a Habbendorf rotary engine be modified so that it is able to achieve maximum performance with the fuels currently available

E. If a car equipped with a Habbendoff rotary engine were to race against a comparable car equipped with a great racing engine, by how much would the performance of the great racing engine surpass that of the Habbendorf rotary engine

简单介绍CVC基本原理？