The multiple choices are meant to throw you off. Answer A would be a popular wrong choice that was picked because a person may have forgotten to think about cases where the function is undefined. Answer B is the range (output, y/f(x) values) excluding -1 and 1 of course. Answer C are all reals excluding the values where sine is zero and consequently tangent is zero. Answer D are all reals excluding the values where cosine is zero and consequently tangent is undefined. Tangent is defined for that region, so that is your answer.