Which of the following is true about United's service?

United Airlines' service includes the staff wearing aprons, which is a common practice among many airlines to maintain a professional appearance. Wearing aprons is practical for cabin crew, as it provides them with a designated way to carry items needed for service, such as pens, service items, or even a small personal item, while also enhancing their professional look. This practice signifies attentiveness and readiness to serve passengers.

In contrast, other options present limitations or inaccuracies about United's onboard service. For example, the airlines typically cater to multiple classes of service beyond economy, and they have varying policies regarding complimentary services depending on the flight and class of travel. Thus, the correct statement about United's service focuses on the professionalism and functionality represented by their wearing of aprons.