Which of the following describe discrete random variables, and which describe continuous random…

Which of the following describe discrete random variables, and which describe continuous random variables?

a. The length of time that an exercise physiologist’s program takes to elevate her client’s heart rate to 140 beats per minute

b. The number of crimes committed on a college campus per year

c. The number of square feet of vacant office space in a large city

d. The number of voters who favor a new tax proposal