What Is One of the Major Differences Between Autistic Disorder

What is one of the major differences between autistic disorder and Asperger's disorder?

A) There are no significant delays in language in Asperger's disorder.
B) There is a greater degree of memory impairment in autistic disorder.
C) People with autistic disorder generally obtain higher intelligence scores.
D) Asperger's disorder tends to develop much earlier than autistic disorder.