time complexity of recursive programs

Consider the vertices V1 and V2 that are simultaneously on the function call stack at some point during the execution of depth-first search from vertex s in a digraph. Which of the following must be true?

I. There exist directed path from s to V1 and directed path from s to V2.
II. There exist both a directed path from V1 to V2 and a directed path from V2 to V1
III. If there is no directed path from V1 to V2 then there exist a directed path from V2 to V1

The number of above statements is/are true ________ .

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