Which of the following sentences uses apostrophes correctly?

What following sentences?

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To determine which sentence uses apostrophes correctly, we need to understand the proper usage of apostrophes. Apostrophes are generally used in two ways: to indicate possession and to form contractions.

Let's examine the given sentences:

1. The cat's tail was fluffy.
2. Its' raining outside.
3. I don't know where they're going.

Sentence 1: "The cat's tail was fluffy."
In this sentence, the apostrophe is used correctly. It indicates possession, showing that the tail belongs to the cat.

Sentence 2: "Its' raining outside."
This sentence does not use the apostrophe correctly. The word "its" is a possessive pronoun and does not require an apostrophe. The correct version should be "It's raining outside," where the apostrophe is used to form the contraction of "it is."

Sentence 3: "I don't know where they're going."
In this sentence, the apostrophe is used correctly to form the contraction of "they are."

Therefore, the correct sentence that uses apostrophes correctly is Sentence 1: "The cat's tail was fluffy."