The coefficients are -3 and 5. They are the numbers to the left of the variable terms Multiply the coefficients to get -3*5 = -15. So -15 is the coefficient in the answer
Multiply the x terms to get x^3 times x = x^(3+1) = x^4. Notice the exponents are being added
Do the same for the y terms as well: y^2 times y^(-1) = y^(2+(-1)) = y^(2-1) = y^1 = y
So we have a final coefficient of -15, the x terms simplify to x^4 and the y terms simplify to just y
Put this all together and we end up with -15x^4y which is what choice C is showing