Explanation : ü Edges with weights 1 and 3 will be selected first,
ü Now bottom edge with weight 4 will not be selected as will cause cycle on MST,
ü both corner vertices have two-two choices to select the vertices, so these corner edges with weights 4 and 5 will resultant 2*2 = 4 MSTs.
So, total number of MSTs are 2*2 = 4, which is answer.
Option (A) is correct.