If 0 < x < 1, which of the following is greatest ?

Answer: Option D

0 < x < 1
⇒ x² < x < 1 ..... (i)
⇒ $$\frac{1}{x^2}$$ > $$\frac{1}{x}$$ > 1 > x > x² [using ...(i)]
Hence, $$\frac{1}{x^2}$$ is the greatest.