Assertion (A): One mole of CO₂ formed when 1 mole of O₂ reacted with 1 mole of CO according to the reaction.

 $2\mathrm{CO}+{\mathrm{O}}_2\to 2{\mathrm{CO}}_2$ 
Reason (R): CO is the limiting reagent in the above reaction.

if (A) is true but (R) is false

if both (A) and (R) are correct and (R) is correct explanation of (A).

if both (A) and (R) are false

if both (A) and (R) are correct but (R) is not the correct explanation of (A).