Babies Born with Low Birth Weights (Less Than 2500 Grams)

Babies born with low birth weights (less than 2500 grams) are at an increased risk for many infant diseases. Researchers in North Carolina collected data to see what variables may influence the birth weight (in grams) of a child, including whether the mother drank alcohol during pregnancy, whether the mother smoked during pregnancy, the mother's age (years) , the gestation of the pregnancy (number of weeks from conception until birth) , the mother's race, the length of the birth (hours) , and several others. The following plot was created to summarize some of the data collected.
-Explain why whether the mother drank alcohol during pregnancy is a confounding variable when trying to determine if smoking increases the risk of low birth weight.

A) Drinking alcohol may be associated with low birth weight, and mothers who drink may be more likely to also smoke.
B) Drinking alcohol may be associated with high birth weight, and mothers who drink may be more likely to also smoke.
C) Drinking alcohol may be associated with low birth weight, and mothers who drink may be less likely to also smoke.
D) None of the above.