Which of the following can be a rationalising factor of $(\sqrt{2} + \sqrt{3} + \sqrt{5})$ ?

$(\sqrt{2} + \sqrt{3} - \sqrt{5}) \sqrt{6}$

For rationalization, we need to multiply the given equation by the given options. If we get a real number by multiplying it then we can choose it as the correct option.

$(\sqrt{2} + \sqrt{3} - \sqrt{5}) \sqrt{6}$

⇒ (2 + \(\sqrt {6}\) - \(\sqrt {10}\)+ \(\sqrt {6}\) + 3 - \(\sqrt {15}\)+ \(\sqrt {10}\)+ \(\sqrt {15}\)- 5) \(\sqrt {6}\)

⇒ (2\(\sqrt {6}\))\(\sqrt {6}\) = 12

Here, 12 is rational number

The rationalising factor of $(\sqrt{2} + \sqrt{3} + \sqrt{5})$ is $(\sqrt{2} + \sqrt{3} - \sqrt{5}) \sqrt{6}$