Converting to a frequency table: 0–10: 3, 10–20: 9, 20–30: 15, 30–40: 30, 40–50: 18, 50–60: 5.
The class with the highest frequency is 30–40.
Answer: (C) 30 – 40
Convert the cumulative frequency table to a regular frequency table by subtracting successive values (e.g., 57 − 27 = 30 for 30–40). The class with the maximum frequency is the modal class. Here, 30–40 has frequency 30, which is the highest — so it is the modal class.