Answer: A long, straight glucose chain (a major constituent of starch)
Explanation: Starch is mostly amylose (straight chain glucose polymer) but has varying amounts of branched glucose chains (amylopectin).
Fatty acids are hydrocarbons with a carboxylic acid group (-COOH) attached, so they are hydrophobic (don't mix with water) at one end and hydrophilic (water soluble at the COOH end)
Simple carboxylic acids don't have a long enough hydrocarbon chain to have this characteristic, e.g. CH3COOH acetic acid
Typical fatty acids found in nature include stearic acid with an 18-carbon chain
CH3-(CH2)16-COOH