Step 1: Grignard reagent reaction.
Grignard reagents react with carbonyl compounds to form an alcohol. In this case, the reaction with the ketone forms a secondary alcohol.
Step 2: Conclusion.
The product is a secondary alcohol, \( \text{CH}_3\text{CH}_2\text{CH}_2\text{C(OH)}\text{CH}_3 \), corresponding to option (3).