Which traversal method for a binary tree does the following Pascal code illustrate
procedure traverse(p:pointer);
begin
it p＜＞nil
then begin
traverse(p↑.left);
process(p);
traverse(p↑.right)
end
end;

A．I-nodes
B．a linked list allocation
C．a continuous allocation
D．a linked list with index

A．Spanning tree of a graph may not be unique.
B．Minimum spanning tree of a graph may not be unique.
C．Finding critical path is an operation on directed graph.
D．Finding critical path is an operation on undirected graph.