Addressing the global challenge of plastic pollution involves the design and use of biodegradable polymers. Poly(3-hydroxybutyrate) (PHB) is a biodegradable polyester produced by bacterial fermentation of sugars. The monomer for PHB is 3-hydroxybutanoic acid, shown below:
Which two functional groups present in this monomer react together to form the ester linkages in PHB?
−CH3-\text{CH}_3−CH3 and −COOH-\text{COOH}−COOH
−OH-\text{OH}−OH and −COOH-\text{COOH}−COOH
−OH-\text{OH}−OH and −C=O-\text{C}=\text{O}−C=O
−CHO-\text{CHO}−CHO and −OH-\text{OH}−OH