The correct answer to this open question is the following.
The video can best extend the information Dr. Dowell gives about careers in disease control in that the video shows the images of Dr. Dowell father while he was treating patients on the island of Haiti.
We are referring to the video "When Birds Get Flue and Cows Go Mad, How Safe We Are?" The video talks about diseases such as the bird flu and the mad cow disease, and how vulnerable humans are to those diseases.
In the video, Dr. Dowell comments that he became interested in becoming a doctor because his father was a doctor. He traveled with his mother and father to Haiti because the father was treating patients from different viruses. ANd with the support of the video, the audience can clearly view the images of the father treating patients and this creates a more vivid impact on the audience.