题目

It is known that teaching little children is no easy job because it ____enough patience and care.A. calls on         B. calls for             C. calls off                            D. calls in 答案：B下列说法中，正确的是（　　）A．两条不相交的直线叫平行线B．一条直线的平行线有且只有一条C．若直线a∥b，a∥c，则b∥cD．两条直线不相交就平行