4: when the neighbor saw this.
it LOOKS like a complete sentence but singling out the fragment by itself you can see it looks funny because it’s unfinished!
<h2>Answer:</h2>
If linking words start a sentence, they are followed by a comma. When they are used to connect two clauses, a semi-colon is used at the end of the first clause, and a comma is often used after the linking word(s).
estuaries
Chesapeake Bay. The Chesapeake Bay is the largest estuary in the United States. It runs north-south from the mouth of the Susquehanna River to the Atlantic Ocean. It is one of the most productive estuaries in the world, with over 3,600 species of animals and plants.
Or is a coordinating conjunction.