Your are right, 
and 2 are solutions.
Of course each of these solutions can be replaced by the same number +k2
(with k being an element of Z) since sin x=sin (x+k2) with k being an element of Z.
Those are angle measures expressed in radians.
If you translate in degrees you basically have to know that radian=180 degrees
so radian=60 degrees and 2=120 degrees. So this two could be values of theta (A and B).
On top of that
could also be a solution (x+k2 with k=1). This can be translated to 60+360=420 degrees which is solution D.
So C. 240 degrees is the only one that could not be a value of theta.
Of course each of these solutions can be replaced by the same number +k2
Those are angle measures expressed in radians.
If you translate in degrees you basically have to know that
so
On top of that
So C. 240 degrees is the only one that could not be a value of theta.
