Organisms or fluids attempting to enter the cell body of a neuron must first pass through the ______

A child's brain reaches ______ of its adult size by about the age of 2

a. one-quarter c. three-quarters b. one half d. one third

When several schemes are combined and coordinated to generate a single act to solve a problem, this is called __________

a) goal-directed behavior b) tertiary circular reaction c) secondary circular reaction d) object-directed behavior