Answer:
B. There is correlation but no direct casual relation, but losing teeth and arithmetic skills.
Step-by-step explanation:
Given:
Correlation between lost of baby teeth and arithmetic skills.
Solution:
Correlation and causality concepts are so used here.
Correlation is the relationship between two variables to get or to predict information.
Correlation is not always causation.
So here the correlation is used to predict the arithmetic skills based on lost teeth.
i.e. More teeth lost more arithmetic skills.
Causality means change in one variable changes value of other variable.
So it gives direct causal relation between the variables.
Here they given relationship between the children lost teeth and arithmetic skills to predict information.
But ,there no actual imply on correlation.
Arithmetic skills can also depends upon third variable.
Hence there is no direct causal relationship between them.
, 
, and 
. We see that the common difference is 
, and 
, so we write,
.