The force has to be in either the same or the direction to the direction of motion for work to be done. what goes in the gap?

The force has to be in either the same or the opposite direction to the direction of motion for work to be done.

to be honest as much as i would love to answer this. i feel as if something's missing. just saying.

hi there if you are asking for conformation that wavelingth is the correct answer is wrong it is the answer is frequency. : )

i hope this you out, have a wonderful day