Scientists have yet to pinpoint the mechanisms involved but have come up with several （        ）explanations.

It was impossible to________ the exact position of the ship. A: discount B: pinpoint C: symbolize D: recruit

After the sinking of the ship, Robinson Crusoe could do nothing but __________ on a piece of wood until he reached an island in the middle of nowhere. A: dwell B: drift C: pinpoint D: sneak