A：I am certain he’ll make it.
B：That’s really tough.
C：Everything is going well with me.
D：Actually, there is no choice anyway.
4+48=____
4+89=____
6+35=____
下列文学常识表述有误的一项是（ ）
某人爬山，从山脚爬上山顶，然后又从原路返回到山脚，上山的平均速率为v1，下山的平均速率为v2，则往返的平均速度的大小和平均速率是( )
