Choose the best form: Look! It square cats and dogs. square rains don't rain is rain

The best form to complete the sentence "Look! It $\square $ cats and dogs." is "is raining."<br /><br />So, the complete sentence would be: "Look! It is raining cats and dogs."<br /><br />The phrase "cats and dogs" is an idiomatic expression used to describe heavy rain. The verb "is raining" correctly indicates the present continuous tense, which is appropriate for describing an ongoing action or event.