I just wanted to know what the question is asking about
So the question states:
Draw a graph, labelling the vertices with letters beginning at A, so that the queue in a Breath First Search of the graph beginning at vertex A would have a maximum length equal to 4.
So I know how a Breadth First Search works but what does it mean that it has a maximum length equal to 4?
Here's a link for your question: https://www.tutorialspoint.com/data_structures_algorithms/breadth_first_traversal.htm
There is the mention of the queue in that explanation and I believe it means the nodes or vertices in that queue cannot be more than four.