Correct usage of commas: http://www.aims.edu/student/online-writing-lab/grammar/comma-rules

A comma should be placed everytime a natural pause is required.

Independent clauses are sentences that can function alone without the requiement of any other additional words.

Coordinating conjunctions can be considered as the "initial"/ "root idea" of a sentence with more than one idea.

When joining two ideas in one sentence, in order for it to be grammatically correct, a comma needs to be placed before the coordinating conjunction.

Decide whether the following sentence is correct or incorrect: I wanted to go on vacations this year, but didn't in the end.

Introductory elements can be considered a linguistic element which represents the natural transitions from one sentence to another

Subordinate clauses, prepositional phrases, and transitional expressions are a type of:

What kind of sentence is the following... "For instance, 100% of the reduced material is used for another function immediately."

What kind of sentence is the following: "As she studied hard throughout the semester, passing wasn't a worry. "

Decide whether the following sentence correct or incorrect: "I bought milk, and sugar in the supermarket"

Decide whether the following sentence correct or incorrect: "She took Spanish, French, and Biology last year."

Decide whether the following sentence correct or incorrect: "He bought an expensive, fast car."

When using quotations (" "), the coma is placed outside the final quotation, when speech continues.

When writing dates, a comma should be placed between the month and the date. For example: "September, 20, 1991."