Children who have lost some baby teeth have better arithmetic skills than children who have not lost any baby teeth. In fact, the more baby teeth a child has lost, the better his/her arithmetic skills tend to be.

Which of the following statements is most likely true?

a. There is a correlation here, and improving arithmetic skills causes the loss of baby teeth.
b. There is a correlation here, but there is not a direct causal relationship between losing baby teeth and arithmetic skills.
c. There is no correlation between arithmetic skills and losing baby teeth.
d. There is a correlation here, and losing baby teeth causes arithmetic skills to improve.