Macroeconomics Is Based on Microeconomics for All of the Following

Macroeconomics is based on microeconomics for all of the following reasons except:

A) when we study the economy as a whole, we must consider the decisions of individual economic actors.
B) aggregate variables are simply the sum of variables describing many individual decisions.
C) macroeconomic decision makers, when they make their choices, are required to maximize utility functions.
D) to understand the determinants of aggregate investment, we must think about a firm's deciding whether to build a new factory.