Which of the following options has the minimum value?

Explanation

On finding the value according to the options, $\sqrt{9} - \sqrt{7} = 3 - 2.645 = 0.355$ $\sqrt{6} - \sqrt{4} = 2.449 - 2 = 0.449$ $\sqrt{18} - 4 = 4.242 - 4 = 0.242$ $\sqrt{28} - 5 = 5.291 - 5 = 0.291$ $0.242 < 0.291 < 0.354 < 0.449$ Therefore, the value of $\sqrt{18} - 4$ is the minimum.