That function, as you have written its definition, is a polynomial in ×. The implicit domain of any polynomial function is the set of all real numbers. Since that is not one of the options, my guess is that you wrote something other than what you meant. Consider editing the expression, and please have a regard for the order of operations.

f(×)= (x + 5)/(2x + 3)

2x + 3 cannot be zero

2x + 3 ≠ 0

x ≠ -3/2

Domain: R - {-3/2}

A. All real numbers except -3/2