The example that represents a discrete data constraint with viable solutions is "number of tests passed."
Discrete data consists of distinct, separate values, often counted in whole numbers (integers), which is the case here as the number of tests passed can only be a whole number (0, 1, 2, etc.).
The other examples, such as "distance between points," "average weight of all the newborns in a hospital ward," and "average score on a test," involve continuous data, which can take on any value within a range.