单位阶跃函数的拉普拉斯变换是()
A.A
B.B
C.C
D.D
参考答案:A
—Does your brother like action movies?
—_____. He thinks they are exciting. [ ]
A. Yes, he does
B. Yes, he is
C. No, he isn't
D. No, he is
下列害虫中,主要为害十字花科蔬菜的是()。
A、菜蛾
B、甘蓝夜蛾
C、菜叶蜂
D、黄条跳甲
E、萝卜蝇