Which sentence uses correct spelling of the homonym?

Janine's baby weighs eight pounds.

Fireflies danced in the knight.

How do I love you; let me count the weighs.

I do knot know him at all.

Janine's baby weighs eight pounds.

Explanation:

The word "knight" in the second sentence is referring to knights, like medieval soldiers, instead of the night, which is when fireflies come out. The third sentence uses "weighs" instead of ways, making it incorrect, as weighs refers to calculating how heavy something is. The use of the word "knot" in the last sentence is also incorrect, as the correct spelling in this case is "not". The first sentence is the only one that has correct spelling and makes sense, therefore it is correct.