Tuesday's Psychology Trivia Question: When Do Humans Have the Largest Number of Brain Cells?

Thought for the Day: Today's psychology trivia question has to do with the development of the brain. Here goes:

           At what age humans have the largest number of brain cells?
                a) 5 years old
                b) 45 years old
                c) 30 years old
                d) 2 years old
                e) 18 years old

Come back on Thursday for the answer.