Which of the following is a geometric construction?

A. finding the line that divides an angle in half
B. finding the complement of an angle
C. finding an angle in a triangle ***
D. finding an exterior angle of a triangle
I think it's C but can someone check please?

no way. If you believe that, suppose you explain how to do it.

In fact, C is the only choice which is on fact not solvable via construction.
But A is probably the choice they want.