Identify each of the following as a catabolic or an anabolic reaction:
a. synthesis of lipids from glycerol and fatty acids
b. glucose adds $\mathrm{P}_{\mathrm{i}}$ to form glucose-6-phosphate
c. hydrolysis of ATP to ADP and $\mathrm{P}_{\mathrm{i}}$
d. digestion of proteins in the stomach