问题
单项选择题
关于离心式压缩机的特点，下列说法错误的是（）
A、运转平稳，操作可靠，备件的需用量小
B、其稳定工况区较窄，气量调节较方便，但经济性差
C、不适用于气量小及压比过高的场合
D、目前离心压缩机的效率高于活塞式压缩机
答案
参考答案：D
搜题请搜索小程序“爱下问搜题”
关于离心式压缩机的特点，下列说法错误的是（）
A、运转平稳，操作可靠，备件的需用量小
B、其稳定工况区较窄，气量调节较方便，但经济性差
C、不适用于气量小及压比过高的场合
D、目前离心压缩机的效率高于活塞式压缩机
参考答案：D
| 完形填空。 | ||||
| Mr. Dawson was an old grouch (脾气坏的人), and everyone in town knew it. 1 knew not to go into his yard to pick an apple, because old Dawson would come after you with his gun. One Friday, 12-year-old Janet was walking out with her friend Amy. They 2 go by Dawson's house, but as they got close Janet saw him 3 on his front porch (门廊) and suggested they cross over the street. Like most, she was 4 of the old man. Amy said not to worry. When they got close enough, Dawson looked up with his usual frown, 5 when he saw it was Amy, he gave a(n) 6 smile. Amy smiled back and told him Janet was 7 overnight with her to listen to music and play games. Dawson told them that sounded fun, and gave them each a(n) 8 . Later, Janet asked Amy:"Everyone says he's the meanest man in town. 9 he was so nice to us?" Amy explained that when she 10 started walking past his house he wasn't very friendly, but she pretended he was wearing a(n) 11 smile and so she always smiled. It took a while, but one day he half-smiled 12 . After a while, he started smiling real smiles and then talked to her. She said he always 14 her an apple now, and is always very kind. "An invisible smile?" questioned Janet. "Yes," answered Amy, "My grandma told me that if I pretended I wasn't 14 and pretended he was smiling an invisible smile at me and I smiled back at him, 15 he would really smile." If we remember that 16 wears an invisible smile, we too will find that most people can't 17 our sunniness after a while. We're always on the go trying to 18 so much, aren't we? It's so easy to get caught up in everyday life that we forget how easily we can bring 19 to ourselves and others. Giving a smile 20 so little efforts; let's make sure that we're not the ones that others have to pretend are wearing invisible smiles. | ||||
|
