Final answer:
The correct answer is c.The discrete variable from the options provided is the number of red marbles in a jar, as it is counted and not measured, unlike the continuous variables weight, distance, and time which are measured.
Step-by-step explanation:
The question posed is concerned with identifying which of the listed options represents a discrete variable. A discrete variable is one that takes on countable values. Among the options provided (weight of students in class, distance traveled between classes, number of red marbles in a jar, time it takes to get to school), the correct answer is c. Number of red marbles in a jar because this value is obtained by counting individual marbles, thus making it discrete.
On the other hand, weight, distance, and time are examples of continuous variables because they are measured and can take on any value within a range. For instance, the weight of a bag of rice and the temperature of a refrigerator vary continuously and hence are measured, not counted. When defining a variable such as X, which might represent a count such as the number of students who do their homework on time, X would be defined as a discrete variable because you are counting the number of students, a countable quantity.