Final answer:
Tarring a skiff refers to sealing it with a tar-like substance to protect it from water, not just for painting or aesthetics.
Step-by-step explanation:
The word tarring in the context of the sentence "I am tarring a little skiff" refers to the process of sealing the boat.
Tarring is an old method where tar or a tar-like substance is applied to the wood of the boat to protect it from water and make it more waterproof.
This is not to be confused with painting, which is primarily for aesthetic purposes, although it can also provide some protection. Therefore, the correct answer is B. Sealing.