Dr Abromowitz Has Done a Study Looking at the Correlation

Dr. Abromowitz has done a study looking at the correlation between depression in children and amount of television they watched. He finds what seems to be a strong, positive correlation between the two. He decides that watching too much T.V. causes children to become depressed. However, he has a third variable problem. Which of the following is an example of a third variable problem?

A) Parental depression is strongly correlated with both children's depression and the amount of T.V. a child watches.
B) Being depressed causes a child to watch too much T.V.
C) Making any conclusions about connections between only two variables.
D) Thinking there is a connection between variables when there is none.