Select the most appropriate option to fill in the blank.
A sailor was __________through the high tides.

The correct option to fill in the blank is sailing.

Explanation:

Let us analyze the meaning of each word in the given options:

1. Sailing: Moving on water in a ship or boat using sails or engine power. In the context of a sailor navigating high tides, "sailing" is the correct and meaningful verb to use.
2. Swelling: Becoming larger or rounder, usually referring to bodily inflammation or waves rising.
3. Selling: Exchanging a commodity or service for money.
4. Ceiling: The upper interior surface of a room.

Therefore, the most appropriate sentence is: "A sailor was sailing through the high tides."