轴瓦不得超过()
A.70℃
B.80℃
C.65℃
参考答案:C
一宇宙空间探测器从某一星球的表面垂直升空,宇宙探测器升空到某一高度,发动机关闭,其速度随时间的变化如图所示.宇宙探测器在该星球表面所能达到的最大高度是 m.该星球表面的重力加速度大小是 m/s2.
This is the second letter that he has ___ him recently.
A.heard from
B.received from
C.heard of
D.got