What criteria is used first during me root port selection process?

During STP root port selection, a nonroot switch first chooses the port with the lowest root path cost. The root path cost is the cumulative cost from that switch to the root bridge. Only if there is a tie does STP move to tie-breakers such as the lowest upstream bridge ID, lowest upstream port ID, and then lowest local port ID. This order matters because many wrong answers jump directly to bridge ID or port ID. Cisco CCNA 200-301 v1.1 Network Access tests STP because root-port and designated-port decisions determine which links forward and which links block in a Layer 2 topology. The root bridge itself has no root port; every nonroot switch selects one best path toward the root. The first and most important criterion is lowest path cost to the root bridge. That makes option B correct.