Explanations:In English grammar, a compound sentence is formed by joining two or more independent clauses. An independent clause is a clause that can stand alone as a complete sentence because it contains both a subject and a predicate. When two independent clauses are joined by a coordinating conjunction (such as "and," "but," "or," "nor," "for," "so," or "yet"), a comma is required before the conjunction to separate the clauses and improve readability.
The coordinating conjunctions are often remembered by the mnemonic "FANBOYS," which stands for For, And, Nor, But, Or, Yet, and So. These conjunctions are used to connect clauses that are closely related in meaning and can stand alone as separate sentences. In the given sentence, "I finished my homework" and "I went to bed" are both independent clauses that can stand alone as complete sentences. Therefore, a comma is required before the coordinating conjunction "and" to properly separate the clauses.
Option B, "I finished my homework, and then I went to bed," is the correct answer because it uses a comma before the coordinating conjunction "and" to separate the two independent clauses. This punctuation correctly indicates the relationship between the clauses and enhances the clarity of the sentence.
Option A, "I finished my homework; and then I went to bed," is incorrect because it uses a semicolon before the coordinating conjunction "and." A semicolon is used to connect two independent clauses without a coordinating conjunction, or in complex lists. In this case, the coordinating conjunction "and" is present, so a semicolon is not appropriate.
Option C, "I finished my homework and then I went to bed," is incorrect because it lacks the comma before the coordinating conjunction "and." This omission can make the sentence harder to read and understand, as the two independent clauses are not properly separated.
Option D, "I finished my homework, then I went to bed," is incorrect because it omits the coordinating conjunction "and" after the comma. While the comma is correctly placed, the coordinating conjunction is necessary to properly connect the two independent clauses in a compound sentence.
Understanding the correct use of commas with coordinating conjunctions is essential for constructing clear and grammatically correct compound sentences. This knowledge is particularly important for students preparing for standardized tests such as the SAT, ACT, TOEFL, and IELTS, where proper punctuation and sentence structure are often assessed.