Kai's Data Suggests That U

Kai's data suggests that U.S.babies who were breastfed longer have higher standardized test scores and higher grades across childhood and adolescence.However,some of this association was explained by the higher average household income among mothers who breastfed longer and among children who had higher academic achievement on average.Yet again,some of the association between breastfeeding duration and academic achievement remained until immune system measures were included.Here,longer breastfeeding was associated with stronger average immune systems,which were,in turn,related to higher academic achievement (through fewer childhood illnesses that can affect grades and test scores) .This hypothetical study demonstrates that

A) moderating variables can sometimes also be confounding variables.
B) confounds explain all of the association between the independent and dependent variables.
C) once a control variable is shown to be a confound,all other added variables will be confounds.
D) some variables in one model can be confounding while others can be mediators.