单选题 Given the following frequency distribution:

Interval	Frequency
10 up to 30	5
30 up to 50	10
50 up to 70	15
70 up to 90	5

Which of the following statements is FALSE? A. The interval size is 20. B. The relative interval frequency of the second interval is 14.28. C. The interval frequency of the third interval is 15.