Velocity is distance over time

. If it wants it in km/h you're good to go otherwise if its m/s you need to convert km to m by multiplying 30 by 1000 and t in hours to seconds by multiplying 0.5 by 3600.
Letter D: The amount of sleep a student gets affects student achievement
Answer: d boiling water
Explanation: the water is boiling and bubbling cause the molecules are so fast and they hit off each other