[tex]\qquad\qquad\huge\underline{{\sf Answer}}[/tex]
Let's solve ~
[tex]\qquad \sf \dashrightarrow \: {x}^{2} = 18[/tex]
[tex]\qquad \sf \dashrightarrow \: {x}^{} = \sqrt{ 18}[/tex]
[tex]\qquad \sf \dashrightarrow \:x = \sqrt{2 \times {3}^{2} } [/tex]
[tex]\qquad \sf \dashrightarrow \:x = 3 \sqrt{2} [/tex]
Therefore, the correct choice will be A
