The terms are $\sqrt{6}$, $\sqrt{24}$, $\sqrt{54}$, i.e., $\sqrt{6}$, $2\sqrt{6}$, $3\sqrt{6}$, … with common difference $\sqrt{6}$. Next term = $4\sqrt{6} = \sqrt{96}$. Answer: (b) $\sqrt{96}$
Rewrite each term: $\sqrt{6}=1\sqrt{6}$, $\sqrt{24}=2\sqrt{6}$, $\sqrt{54}=3\sqrt{6}$. The AP has $d=\sqrt{6}$, so the 4th term is $4\sqrt{6}=\sqrt{96}$. Always simplify surd terms to spot the pattern.