What pronoun will replace the word sky?

There isn't a single perfect pronoun to replace "sky" because the best choice depends on the context. Here are some options:

It: This is the most common pronoun to use if you're talking about the sky as a whole. For example: "The sky was a beautiful blue. It was so clear."

Its: This is the possessive form of "it" and can be used when referring to something belonging to the sky. For example: "The sun painted its colors across the sky."

That: This pronoun can be used to refer to the sky specifically, especially if you're already talking about it. For example: "Look at that! The sky is full of stars."

There: This pronoun can be used to refer to a location in the sky. For example: "I saw a bird flying high up there in the sky."

Which: This pronoun can be used to refer to the sky in a more specific way, especially if you're making a comparison. For example: "The sky, which was once clear, is now covered in clouds."

Ultimately, the best pronoun to use will depend on the specific sentence and the context in which it is used.