The source of electromagnetic waves can be a charge.

Options

A. moving with a constant velocity
B. moving in a circular orbit
C. at rest
D. falling in an electric field

Answer

B, D

Explanation

Here in option (b) charged is moving in a circular orbit. In circular motion , the direction of the motion of charge is changing continuously , thus it is an accelerated motion and this option is correct.
Also we know that a charged starts accelerating when it falls in an electric field.