Better sentence-writing in 30 minutes a day - Dianna Campbell 1995

Type 3: Fragment related to embedding
A sentence-combining approach to the problem of fragments
Sentence combining: basic strategies and common problems

Another type of fragment comes from a slipup in the embedding process. Here are three examples:

(a) The superstition that amethysts prevented drunkenness. Was widely believed by people in ancient times.

(b) A person who spills pepper. Is probably going to get into an argument with a good friend.

(c) Tattoos, which some sailors considered protection against drowning. At one time were also thought to prevent smallpox.

After all the work you’ve done with embedding, the problem with these fragments should be clear. Each lettered item really contains two fragments. Each contains a subject that is set up as a full sentence and a predicate that is set up as a full sentence. To correct them, all you have to do is change capitalization and punctuation.

Another kind of fragment is a variation of this type. It begins with a relative pronoun, and it describes a noun or pronoun at the end of the sentence before it. For example:

The pepper was spilled by Pat. Who any minute might find himself in an argument with his best friend John.

To solve the fragment, change the period to a comma and make the capital W on Who lowercase.

Another way to avoid fragments that involve relative pronouns is simply to keep this rule in mind: The only sentences that can begin with relative pronouns are questions. These, for example, are perfectly fine. They’re not fragments:

Who wrote Jitterbug Perfume?

Whose size 13 shoes are these?

Which pasta recipe works best?