Which option always require a comma before the conjunction

The option that always requires a comma before the conjunction is coordinating conjunction when joining two independent clauses in a compound sentence.

When using a coordinating conjunction (such as "and," "but," "or," "nor," "for," "so," or "yet") to connect two independent clauses in a sentence, a comma should always be placed before the conjunction.

For example:
- "I went to the store, and I bought some groceries."
- "She studied all night, but she still failed the test."
- "He can choose to stay home, or he can come with us."

The option that always requires a comma before the conjunction is when you have two independent clauses joined by a coordinating conjunction.

An independent clause is a group of words that can stand alone as a complete sentence, expressing a complete thought. A coordinating conjunction is a word that connects two equal parts of a sentence, such as "and," "but," "or," "nor," "for," "so," or "yet."

To determine if a comma is necessary before the conjunction, you need to check if both parts of the sentence can function as independent clauses on their own. If each part can be a sentence by itself, then you should use a comma before the coordinating conjunction.

For example:
- "I went to the store, and I bought some groceries."
- "She studied hard for the exam, yet she still didn't pass."

In both of these examples, each part before and after the coordinating conjunction can function as a complete sentence. Therefore, a comma is needed before the coordinating conjunction "and" and "yet" respectively.