Tim told us that his company ______ robots to do some of the work.
A:uses
B:will use
C:has used
D:would use
若关于x的方程1x-3+3=kx-43-x无解,则k=____ .
某物体以30m/s的初速度竖直上抛,不计空气阻力,g取10m/s2.4s内物体的( )