The correct option is D 6 cm
Given, area of an equilateral triangle = 9√3cm2
∵ Area of an equilateral triangle =√34(Side)2
⇒ √34(Side)2=9√3
⇒ (Side)2=36
∴ Side=6cm
[taking positive square root because side is always positive]
Hence, the length of an equilateral triangle is 6cm.