To prove |x + y| ≤ |x| + |y|, we need to divide (x, y) into four cases. Which of the following case groups is inconsistent?
1) x ≤ 0, y < 0, x > 0, y ≥ 0, x > 0, y < 0, and x ≤ 0, y ≥ 0
2) x ≥ 0, y > 0, x < 0, y ≥ 0, x ≥ 0, y ≤ 0, and x < 0, y < 0
3) x ≥ 0, y ≥ 0, x ≥ 0, y < 0, x < 0, y ≥ 0, and x < 0, y < 0
4) x ≤ 0, y ≤ 0, x ≤ 0, y > 0, x > 0, y ≤ 0, and x > 0, y > 0