Answer: The correct option is B, i.e., BD.
Step-by-step explanation:
To find the minimal spanning tree we have Kruskal's Algorithm. In this algorithm we have to select the cheapest edge from the graph. Then connecting the remaining vertices through other cheapest edges, to get minimal spannig tree.
The line segment connecting two vertices is called an edge.
From the given graph it is easily noticed that the edge BD is cheapest edge with length 2.
The length of edge AB is 3, the length of edge AC is 6 and the length of edge EF 4.
Since we have to start with the cheapest edge therefore option B is correct.