Which of the Following Has NOT Been Found as Evidence

Which of the following has NOT been found as evidence in favour of a biological theory of autism spectrum disorder?

A) The brains of people with autism spectrum disorder have been found to smaller and lighter.
B) About 30% of adolescents with autism spectrum disorder have epileptic seizures.
C) Abnormal levels of serotonin are found in 30-50% of autistic children.
D) Symptoms of autism spectrum disorder appear in all cultures.
E) A history of prenatal infection and problems during pregnancy are fairly common among mothers of autistic children.