An indicator 'X' is used for studying the effect of variation in concentration of iodide on the rate of reaction of iodide ion with H$$_2$$O$$_2$$ at room temp. The indicator 'X' forms blue colored complex with compound 'A' present in the solution. The indicator 'X' and compound 'A' respectively are

This question is about the iodine clock reaction, where iodide ions react with H$$_2$$O$$_2$$.

The reaction:

$$\text{H}_2\text{O}_2 + 2\text{I}^- + 2\text{H}^+ \to \text{I}_2 + 2\text{H}_2\text{O}$$

Identifying the indicator X:

The indicator forms a blue colored complex with a compound present in the solution. The well-known indicator that forms a deep blue complex is starch.

Identifying compound A:

Starch forms a blue complex specifically with iodine (I$$_2$$), which is the product of the reaction between iodide and hydrogen peroxide.

The appearance of the blue color indicates that free iodine has been produced, which is used to study the rate of the reaction.

Therefore, indicator X = Starch and compound A = Iodine.

The correct answer is Option 1: Starch and iodine.