Which of the Following Statements Best Describes Findings from the Study

Which of the following statements best describes findings from the study of siblings and the effects of birth order?

A) Research indicates that intelligence becomes diluted with more children in the family.
B) Robust effects have not been found for sibling differences based solely on birth order.
C) Undeniable data reveal that available resources account for different child outcomes.
D) Evolutionary pressures to survive account for similarity in firstborns and later-borns.