31. One kind of tools which are in common use for daily maintenance works on the ship can be used to loosen or tighten a nut or bolt. It has a "jaw" (the part into which the nut or bolt goes) which is of adjustable size, which allows for different size nuts and bolts to be handled by the same spanner. What tool is above description? (A) Open-end spanner (B) Adjustable spanner (C) Pliers (D) Ring spanner