Choose the correctly punctuated sentence.

It's raining outside; take an umbrella is the correctly punctuated sentence. This sentence effectively uses a semicolon to connect two closely related independent clauses. The semicolon indicates a pause that is stronger than a comma but not as final as a period, thus allowing the reader to understand that the two ideas are linked: the fact that it is raining and the suggestion to take an umbrella as a result.

In contrast, the other options fail to use appropriate punctuation that reflects the relationship between the two clauses. The first option, "Its raining outside, take an umbrella," is incorrect because it lacks an apostrophe in "It's," which is a contraction for "it is." The second option, "It's raining outside take an umbrella," is missing necessary punctuation to separate the two independent clauses, making it a run-on sentence. The fourth option, "It's raining outside: take an umbrella," misuses the colon. A colon typically introduces a list or elaboration, which is not the case here.

Understanding how to choose correctly punctuated sentences is essential for clear communication in written English, especially in competitive exams where precision is key. Proper punctuation not only clarifies meaning but also enhances the readability of your writing. Mastery of punctuation rules, such as the correct use of semicolons, can significantly improve your performance in language-related sections of competitive exams.