The correct answer is B. So for A, 8m is smaller than 12 m. For B, 20 m is Bigger. For C, Find how many meters is 1 centimeter, the answer is 1 cm : 12m, the meter is not bigger than 12, but the same, so C is wrong. For D, divide both sides by 3 to find 1 CM, the answer is 1 cm : 5 m, it is wrong.