The correct answer is D. however.
You want to show contrast between these two sentences, and the only word among these which can do that is <em>however. </em>The sentences are each other's opposites - even though there is an increase of eagles in the Southeast, there is still a decline in their numbers overall.
APEX 2018- C.) The Desire to improve education leads to a future in which students have to take aptitude tests as early as preschool.
