电力，汽油，核聚变燃料，沼气、余热等属于二次能源。

[A] dictionary

[B] soldier

[C] computer

[D] music

[E] supermarket

[F] street

[G] plane

People listen to it.

根据首字母填空。

1. My pen pal is from Tokyo, J____.

2. --Does she work in a b____?  

   --Yes. People give their money to her or get their money from her.

3. Ask me if you are not s____ how to do it.

4. Mr. Green is  fifty years' old, but he looks very  y____．

5.E____ have long noses.

女性，76岁。反复咳嗽、咳痰伴喘息20余年，活动后气短5年，间断双下肢水肿1年，加重伴心悸1周。吸烟史30余年。查体：口唇发绀，桶状胸，双肺呼吸音粗，可闻及散在干啰音，双肺底可闻及水泡音，肝肋下2cm，双下肢凹陷性水肿。

以下对明确诊断最有帮助的检查为（）

A.胸片

B.心电图

C.血常规

D.肺功能

E.血气分析

There _______ two books and a pen on the desk.

A．is

B．are

C．be

D．has

正弦交流电的三要素是什么？并简要说明。