The safe height (h) to diameter D. ratio (i.e., h/d) for liquid/petro fuel storage tank of capacity more than 45 kilolitres is less than _________________?

The safe height (h) to diameter D. ratio (i.e., h/d) for liquid/petro fuel storage tank of capacity more than 45 kilolitres is less than _________________?

A. 1
B. 2
C. 3
D. 3.5