A recent headline reads "Early Language Skills Reduce Preschool Tantrums, Study Finds," and the article offers a potential explanation for this: "Verbalizing their frustrations may help little ones cope." The article refers to a study that recorded the language skill level and the number of tantrums of a sample of preschoolers, and found that those with better early language skills had fewer tantrums. Assume that the sample used is representative of the population of all toddlers.

a. Is this an observational study or a randomized experiment?
b. The statement "Early Language Skills Reduce Preschool Tantrums" implies causality. Assuming that researchers found an association between these variables, can we conclude causality from this study? Explain based on the methodology of the study. Rewrite the statement "Early Language Skills Reduce Preschool Tantrums" in a way that does not imply causality.
c. Give a potential confounding variable that relates to this study.
d. Explain how your confounding variable is associated with both the explanatory and the response variables.