China is a great country. For one thing, she has a long history with much knowledge; _______, she is developing rapidly in her own way. A. second B. the second C. f
How to Make Friends Friendship is a very important human relationship and everyone needs good friends. Good friendship has many benefits. It offers companionship, improves self-worth and promotes go
如图12－2表示一交流电的电流随时间而变化的图象，此交流电的有效值是： （ ）
算出结果为D