用电动机起动发动机是以电动机作为动力，它以（）为电源。
Ａ、直流电
Ｂ、交流电
Ｃ、交直流电
Ｄ、电动机
参考答案：A
用方框内所给词的适当形式填空。
1. I ________ to ride a bike when I was four years old.
2. Students usually ________ learning English in primary schools.
3. They ________ a big party to celebrate （庆祝） the harvest last October.
4. Professor Li stopped ______ after he had a heart disease.
5. I ________ Lucy last night, but she was not at home.
按图Ⅰ—26所示回答下列问题：
左视图采用了（）剖视。
