It won't do you any good to simply supply the answer
Every trig student should have graph of cos(x) (as well as sin(x)) firmly in their mind. Go to a graphic calculator, https://www.desmos.com/calculator is a good one. Investigate the cos graph, and the sin while you're at it!
Your question should specify a range for the angle because in fact there are an infinite number of places where the cos(x) = 0 since it is a cyclic curve. I think we can assume that the range is [0, 2PI]
Robert K.
The statement the problem has a 0 and a pi next to the question -- presumably as possible answers. (different from the 4 multiple choice options although both included) so I am telling you that 0 is the correct answer and pi is incorrect.05/30/22