The correct option is B 12 squares with side 1 m each
We know that area of square = (side)2
Option A has square of side 12 m, that means its area =(12m)2=144m2
Option B has 12 squares of side 1 m each, that means its area =12×(1m)2=12m2
Option C has 3 squares of side 4 m each, that means its area=3×(4m)2=48m2
Option D has 4 squares of side 3 m each, that means its area=4×(3m)2=36m2
Hence, option B is the correct one.