Which Statement Illustrates Evidence That Intellectual Disability Probably Has Environmental

Which statement illustrates evidence that intellectual disability probably has environmental causes

A)  Most individuals with mild intellectual disability are from lower socioeconomic classes which exposes them to unfavourable environments. 
B)  Most individuals with profound intellectual disability are from higher socioeconomic classes. 
C)  Most individuals in lower socioeconomic classes have IQs lower than 100. 
D)  Most individuals with Down syndrome are from higher socioeconomic classes.