Why must an air traffic controller know a plane's velocity

1. In order to prevent collision

2. To be able to control free flow of air traffic

Explanation:

The reason why it's paramount for air traffic controller to know the velocity of a plane is to enable them to avoid or prevent collision of planes coming in opposite direction. Knowing the velocity of the plane by the air controller would also give the air controller a good insight of how the air traffic should flow in oder to avoid accidents and disorderliness.

the answer is c

tell me if wrong

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.