Answer:
The answer is 2 levels
Step-by-step explanation:
There are two levels in this case because the experiment in question here compares how two sleep levels, which can be said to be the experimental sleep level of 11 hours, and the control sleep level of 8 hours. Basically the type of treatment provided in the question has two levels: control and experimental. This entails that if an experiment was designed to compare 4 types of meal, then such experiment can be said to have 4 levels of independent variables.