刺背技术是由()向()的角度刺。
参考答案:上;下
--- Remember to spend some time _____ your loved ones ,because they’re not going to be around forever .
--- OK.
A.from
B.with
C.in
D.on
圆的周长是这个圆的半径的2π倍.______.(判断对错,并改正)