In packed towers provided with pall rings liquid redistributors are positioned at heights of every 6 metres or 5-10 times the column diameter, whichever is less. Maximum size of the pall rings should not exceed _______________________ of the column diameter?
A. 1/10-1/15th
B. 1/5-1/10th
C. 1/20-1/30th
D. 1/2 to 1/4th