What is the difference between speed and velocity with regards to uniform circular motion?

Speed ignores the direction of motion and is a scalar quantity. Velocity requires a directional component (like the arrow in a vector). In circular motion, the speed remains the same but the velocity is constantly changing since the direction of motion is constantly changing (ie. it is accelerating).

Wavelength divides in half and speed stays the same.

If its history of, then b) because a) implies only present day (now)