Which sentence demonstrates the correct use of the semicolon?

Since Margo always arrives late; we were not concerned when our 12 o'clock meeting time came and
went.

There are three key ingredients in what is known as "the trinity" in Cajun cooking; onions, celery, and
green pepper.

Some people like to cook their own meals; others prefer to dine out or have their meals delivered.

Erica has two dogs; and she completely spoils them with treats, toys, and trips to the dog park.