B. Overgeneralization
They are saying that "practically every teen cares" but have no real evidence to back that up. They may have polled a small group of teenagers and because the majority of them said they care about animals they generalized that information to represent everyone in the age group. Without a full poll or teens there is no way to know how many do or do not care about the welfare of animals.
Answer: Intelligent
Explanation: The definition of sagacious is "having or showing keen mental discernment and good judgment; shrewd."
