Who is they?
The shipping company harvests lobster for their business, because they receive a high demand for this type of seafood.

A:
The shipping company

Who is they?
Walmart is promoting their Black Friday sale heavily in commercials, since they are the best medium to get information out to the average consumer.

A:
commercials

Who is it?
A motorboat turns the propeller pushing the water backwards, thus it moves forward.

A:

A motorboat