The marks (out of 100) obtained by 50 students are to be arranged in equal-width, continuous classes. Which of the following sets of class intervals is continuous and has no overlap?
a) 0–9,10–19,20–29,30–39
b) 0–10,11–21,22–32,33–43
c) 0–10,10–20,20–30,30–40
d) 0–9,9–18,18–27,27–36