The correct answer is A) Adjust-a-matic tensioner. The adjust-a-matic tensioner is the proper tensioning device used with wire rope lashing to secure vehicles aboard Ro-Ro (roll-on/roll-off) vessels. This type of tensioner allows for easy adjustment and maintenance of the proper tension in the wire rope lashings, which is critical for safely securing the vehicles during ocean transport. The other options are incorrect because: B) Buckle tensioners are not suitable for wire rope, C) Ratchet tensioners are typically used for chain lashings, not wire rope, and D) Chain levers are used to tension chain, not wire rope lashings.