The correct option is A 225 rounds
The number of rounds (R) fired in an hour is directly proportional to the number of tankers (T) used.
Let the constant of variation be k.
Given, when R = 45, T = 9.
So, k=RT =459=5.
Hence, the number of rounds (R) fired by 45 such tankers in a shot = kT = (5)(45) = 225 rounds.