Which of the following rational expressions is in lowest terms?
x2−4x−2\frac{x^2 - 4}{x - 2}x−2x2−4
x2+5x+6x+3\frac{x^2 + 5x + 6}{x + 3}x+3x2+5x+6
x+5x+7\frac{x + 5}{x + 7}x+7x+5
2x2+42x+4\frac{2x^2 + 4}{2x + 4}2x+42x2+4