G3PDH is an enzyme needed for glycolysis, while lactase is an enzyme required to digest the sugar lactose. The figure shows mRNA from these genes in mice at different ages. Which is a reasonable argument based on these data?
a. Over time, the amount of lactase enzyme in mice increases because lactase gene expression increases over time.
b. Over time, the amount of G3PDH enzyme in mice increases because G3PDH gene expression increases over time.
c. At four weeks, mice can break down glucose, but not lactose, because G3PDH mRNA is present, but lactase mRNA is absent.
d. At four weeks, mice can use lactase to break down lactose because mice express the lactase gene.