digraph virt {
    graph [nodesep=1.5, rankdir=BT];

    W1 [label = "W", shape=plaintext, height=.1, fontsize=24];
    V [shape=plaintext, height=.1, fontsize=24];
    W2 [label = "W", shape=plaintext, height=.1, fontsize=24];
    B [shape=plaintext, height=.1, fontsize=24];
    C [shape=plaintext, height=.1, fontsize=24];
    D [shape=plaintext, height=.1, fontsize=24];

    D -> B;
    D -> C;
    B -> V;
    C -> V;
    B -> W1;
    C -> W2;
}