Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

Assuming no changes in other variables, which of the following would decrease ROA?
Option A:A decrease in the effective tax rate.
Option B:A decrease in interest expense.
Option C:An increase in average assets.

Answer: C