Final answer:
The diet with foods like broth, jello, and black coffee is a liquid diet, used for medical reasons and should be monitored by a healthcare professional.
Step-by-step explanation:
The diet that includes items such as broth, jello, popsicles, and black coffee is most commonly known as a liquid diet. This type of diet consists of liquids, or foods that turn to liquid at room temperature, and is sometimes used for medical purposes such as preparing for a test or procedure, or for digestive system rest after surgery. It generally does not provide all the nutrients one would need for long-term consumption, and it's important to only follow such a diet if recommended and monitored by a healthcare professional.