Which option is an example of a survey?
A collecting data on pulse rate of a group of people
B. Flipping a coin 100 times and counting the number of heads
C. Asking kids in a kindergarten classroom about the average number of pieces of fruit they eat each day
D. Having a randomly selected group of students take a penci-and paper test and comparing the results with another randomly selected group of students who took the same test on the Computer ​