Basic solution of fructose contains

You are correct. The answer is (3) glucose, fructose, and mannose.

When fructose is dissolved in a basic solution, it undergoes a reversible isomerization reaction to form mannose. This reaction is catalyzed by the enzyme ketose-fructose isomerization.

Therefore, a basic solution of fructose will contain all three sugars: glucose, fructose, and mannose.

Options (1), (2), and (4) are incorrect because they do not contain all three sugars.