较易发生先天缺失的恒牙是A．上下第一磨牙 B．上下第二磨牙 C．上下中切牙 D．上下

阅读理解。

     I had a summer camp with my classmates last year.

     Early in the morning. We gathered at the bus station. After saying goodbye to our parents,we got

on the buses. It took us more than two hours to arrive at the campground.

     We got off the buses cheerfully. Laughing and shouting.We jumped and ran all over the place. It

was the first time for us to be away from the parents.Some of us started to feel homesick(想家).

However, when the night party and dances began, the homesickness was gone.

      The next day, everybody rushed to the boating class, hoping to be at the head of the others. At

first,my friends and I worked hard, but the boat wouldn't listen to us and kept going round and round.

Then the teacher taught us how to work together. After many tries,we did much better.

      Swimming class was my favourite. It was about the hottest time of a day and the best time to stay

in the cool water. The swimming teacher was a funny man, and during the class he often made us laugh

happily.

During the week I learned a lot of new things and made many new friends. I also learned how to take

care of myself.

1.They got to the campground_______.

A. on foot      

B. by bike      

C. by bus      

D. by plane

2. The campground was ______ from their homes.

A. quite near      

B. not far      

C. very long    

D. quite far

3.Why swimming class was the writer's favourite?

A.Because it was good to stay in the cool water when the weather was hot.

B. Because the writer felt quite relaxed during the class.

C. Because the swimming teacher was interesting.      

D.Because of all the above

64.Which statement is NOT true?

A.he children were happy to be away from Dad and Mum.

B.Their homesickness lasted for long.

C.It was teamwork to boat.  

D.They camped for a week.

65.Which is the best title for the passage?

A. I Learnt a lot.  

B. Boating and Swimming.

C. On the Campground  

D. My First Summer Camp

牵引变电所的功能是将110kV或220kV三相交流电变换成（），并供电给牵引网和电力机车。

A.27.5（或55）kV单相交流电

B.27.5（或55）kV三相交流电

C.25kV单相交流电

D.以上答案都不对。

施工人员在停工后改做其他工作的，应( )。

A．适当补偿降效损失
B．按停工损失计算
C．按停工损失的一半计算
D．不给予补偿降效损失

简述商品销售收入确认的五个条件有哪些

简述指纹（乳突花纹的）基本类型。