If you are designing options items for this question "In the past year, how many times did you witness unethical activities in marketing research practices? which of the following designs is the best
a-0, 1-5 times, 6-10 times, 10-15 times, more than 15 times
b-0, 1-5 times, 6-9 times, 10-15 times, more than 15 times
c-Never, Occasionally, Sometimes, Frequently, All the Time
d-0, 1-50 times, 51-100 times, 101-150 times, more than 150 times