A stop-smoking booklet says, “Children of mothers who smoked during pregnancy scored nine points lower on intelligence tests at ages three and four than children of nonsmokers.” Suggest some lurking variables that may help explain the association between smoking during pregnancy and children’s later test scores. The association by itself is not good evidence that mothers’ smokinglower scores. (Select all that apply.)The diet of the child.The psychological condition of the child.The IQ of the mother.The socioeconomic status of the mother.