A. in itself B. to itself C. by itself D. of itself
A. 发射极正偏,集电极反偏 B. 发射极反偏,集电极正偏 C. 发射结正偏,集电结反偏 D. 发射结反偏,集电结正偏
A. 落煤点不正 B. 皮带太紧 C. 皮带太松