光是一种电磁波,它在真空中的传播速度是____ m/s。
3×108
Even though Jane told him to leave her alone, her father still her to the doctor.
A.looked
B.obeyed
C.envied
D.accompanied
预测和效果检验孔只能以整个孔为单位作结论,凡是钻孔中任意一段超标,该孔定为()孔。