In the given sentences, option b is a sentence fragment. A sentence fragment is an incomplete sentence that does not express a complete thought. It lacks a subject, a verb, or both.
Option a: "The restaurant doubled its waitstaff. It wanted to provide good service." is a complete sentence because it has both a subject (the restaurant) and a verb (doubled).
Option b: "The restaurant doubled its wait staff. To provide good service." is a sentence fragment because it does not have a subject. It starts with the phrase "To provide good service," which is not a complete sentence on its own.
To fix the sentence fragment, you can combine the fragment with the previous complete sentence to form a complete thought. For example: "The restaurant doubled its wait staff to provide good service."
I hope this helps! Please feel free to ask any questions if necessary. :)