Final answer:
The channel control strategy being used in this advertisement is influencer marketing.
Step-by-step explanation:
The channel control strategy being used in this advertisement is influencer marketing. The University of Chicago Hospitals is using the testimonial of an intensive care nurse to influence potential patients and promote their services. By featuring a healthcare professional who is employed at the hospital, they are conveying a message of trust and expertise. This strategy aims to convince people that choosing a health insurance plan that includes the University of Chicago Hospitals would be a wise decision.