It should be 5.
The first three edges that would be selected are of costs 11,12,12 ie. AD, AB, BE.
Now remaining 5 edges are of same cost 13 and one edge is of cost 15(this should not be considered ). From these edges we have to select 2 for a Minimum spanning tree. Clearly DE would produce a cycle here. So out of remaining 4 we have to select two.It can be done in 4c2 ways which is 6. But if we add BC and EC together it would produce a cycle. So it should be ignored and leaves us with 5 choices.
So the answer is 5.