Rates of Autism Spectrum Disorder Have Recently

Rates of autism spectrum disorder have recently:

A) decreased,which suggests that there are many children with the disorder who are undiagnosed.
B) decreased,which is probably due to the fact that physicians are reluctant to negatively label children.
C) increased,which likely corresponds to an actual increase in cases.
D) increased,which is probably due to the recent recognition and diagnosis of milder cases.