Why Do We Use "Fast and Frugal Heuristics," According to Gigerenzer

Why do we use "fast and frugal heuristics," according to Gigerenzer

A)  We typically make decisions under divided attention, so we don't focus on the actual problem. 
B)  Most of us do not have the cognitive power to process all the necessary information to make a decision. 
C)  We learn as children to use our best guess, rather than reason through the process. 
D)  We often don't have the time required to calculate every possible outcome or factor.