Would you use the adjacency matrix structure or the adjacency list structure in each of the following cases? Justify your choice.

a. The graph has 10,000 vertices and 50,000 edges, and it is important to use as little space as possible.

b. The graph has 10,000 vertices and 50,000,000 edges, and it is important to use as little space as possible.

c. You need to answer the query getEdge(u, v) as fast as possible, no matter how much space you use.