What is the solution set of the equation: x^2 + 4x +3 = 0

The solution set of the equation: x² + 4x +3 = 0

(A) {1, 3}
(B) {-1, 3}
(C) {1, -3}
(D) {-1, -3}

The answer is: (D) {-1, -3}