问题
单项选择题
石英晶体谐振于并联谐振频率fp时，相当于LC回路的（）.
A.串联谐振现象
B.并联谐振现象
C.自激现象
D.失谐现象
答案
参考答案：B
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石英晶体谐振于并联谐振频率fp时，相当于LC回路的（）.
A.串联谐振现象
B.并联谐振现象
C.自激现象
D.失谐现象
参考答案：B
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| After a long day at school, I walked home with my heavy schoolbag. Sleepy and 1 , I threw my things on the couch and  grabbed something from the 2 to eat. I passed by the living room and wished I could watch TV, but I knew my 3 would take me the whole night. I took my schoolbag and went 4 to my room. I tried to understand chemistry and 5 sleepiness at the same time. I was stressed out and 6 . I wanted something to cheer me up. Later, I 7 the sound of the front door opening. And I waited for it-the sound of my mom singing. 8 she sings off-key(跑调), it made me excited that she was here. I ran down to greet my mom. We 9 each other and I ran back ups   tairs. I like it when my mom was happy. Her 10 flowed down to me and I got the strength to 11 the stress again. Sometimes. I wonder how my mom can still be 12 after coming back from work. Every weekday, she wak  es up 13 in the morning to go to work and spends all hour on the bus before getting downtown.At a 14 factory, she works standing for the whole day and draws patterns for clothes over and over. After work, she gets stuck in 15 for two hours on her way back home. When I 16 my school life with her work life. I should not be the one to 17 . At least I have some interesting things to do at school, but one mistake at work can cost my mom her iob. I 18 that my mom has a positive attitude and lives her life with a joyous heart, though there may be 19 . Seeing her happy makes me feel 20 , too. | ||||
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