A:how often are we going to be away
B:how often we are going to be away
C:how long are we going to be away
D:how long we are going to be away
⑴一条射线上只有一个点,一条线段上有两个点;
⑵一条射线把一个角分成两个角,这条射线叫这个角的平分线;
⑶连结两点的线段叫做两点之间的距离;
⑷20°50ˊ=20.5°;
⑸互余且相等的两个角都是45°.