Which compound is not a carboxylic acid?

Step - 1Option - 1CH3COOH is a carboxylic acidStep - 2Option - 2HO−C||O−CH2−CH3 is a carboxylic acidStep - 3Option - 3CH3−C||O−CH2−OH is a ketone, not a carboxylic acid[Step 4]:Option (4) CH3−CH2−CH2−C||O−OH is a carboxylic acid