The numbers of hours worked (per week) by 400 statistics students are shown below. ​ The percentage of students who work at least 20 hours per week is

A) 25%.
B) 50%.
C) 75%.
D) 100%.

To find the percentage of students who work at least 20 hours per week, we need to count the number of students who work at least 20 hours per week, divide that number by the total number of students, and then multiply by 100 to get the percentage.

Looking at the graph, we can see that there are 300 students who work at least 20 hours per week (200 between 20-29 hours and 100 at 30+ hours), out of a total of 400 students.

So the percentage of students who work at least 20 hours per week is:
(300/400) x 100% = 75%

Therefore, the answer is C.