题目

下列现象中不属于动物之间通讯的是  A．兔子逃跑时竖起尾巴        B．乌鸦筑巢  C．鸟类逃跑时发出鸣叫        D．蚂蚁外出时用分泌物标记路线   答案：BWe have four classes ______ the morning.A. of B. at C. on D. In