Question

the physical quantity which changes continuously during uniform circular motion

Answer 1

Velocity is the physical quantity which changes continuously during uniform circular motion. This is because in the uniform circular motion though the magnitude of velocity remains the same but the direction continuously changes according to the tangent of circle which results in the change in velocity.

Answer 2

It is the velocity which changes continuously during uniform circular motion as it is a vector quantity having direction and magnitude as well.
And in circular motion, in each point the direction is different.