Select the most appropriate option to fill in the blank.
The ________ in my shoelace created a lot of trouble.

The correct answer is knot.

Explanation:
Let us look at the meanings of the given words:

1. knot: A fastening made by tying a piece of string, rope, or shoelace. In the context of shoelaces, a tight or tangled knot causes difficulty in untying, creating trouble.
2. not: Used to express negation or refusal (e.g., "I am not going").
3. naught: Means nothing or zero.
4. nought: A variant spelling of "naught", representing the digit zero (0).

Therefore, the homophone that correctly fits the context of shoelaces is knot.