Final answer:
To address incomplete sentences, use one or two dashes, which can set off or emphasize content, denote a pause or a redirection. Dashes are useful for emphasis, while parentheses de-emphasize content. Fragmented sentences can be stylistic devices if used intentionally.
Step-by-step explanation:
Use one or two dashes for incomplete sentences regardless of verbatim. A dash can be used to set off or emphasize the content within a sentence, marking a contrast, pause, or a shift in direction. Examples of dash usage often involve setting off nonessential information or emphasizing a part of the sentence that requires more attention.
For instance, in the sentence 'The U.S.S. Constitution became known as "Old Ironsides" during the War of 1812—during which the cannonballs fired from the British H.M.S. Guerriere merely bounced off the sides of the Constitution,' the dash sets off an appositive phrase that contains important additional information. Contrastingly, parentheses are used to de-emphasize content, providing less significant details or clarification.
Remember, fragmented sentences can also be employed for stylistic purposes, such as creating a particular effect or tone within your writing. However, it's important to use them sparingly and with clear intention, so they are not perceived as grammatical mistakes.