One Important Reason That Research on Infant Cognitive Abilities Is

One important reason that research on infant cognitive abilities is difficult to conduct is that

A) infants do not have measurable memory skills until 6 months of age, so we cannot assess other cognitive abilities that depend on memory.
B) infants under the age of 3 months are too young to participate in research.
C) it's difficult to assess cognitive processes because of infants' limited motor and language skills.
D) psychologists have typically concentrated on perceptual abilities, rather than cognitive abilities.