One mole of gas A with molecular diameter 2d and average molecular speed v, is placed inside a certain container. Two moles of gas B with molecular diameter d and average molecular speed 2v is placed in an identical container. Ratio of average collision rate of gas A within its container to the average collision rate of gas B within its container is (A)1:3 (B)1:1 (C)3:1 (D)2:1.