Final answer:
The statement about using quotes or hyphens based on the length of an adjective phrase is false; hyphens join words as a single modifier, while quotes are used for titles of shorter works or speech.
Step-by-step explanation:
The statement "If the adjective phrase is longer than six words, use quotes; if shorter than six words, use hyphens" is false.
In English grammar and punctuation, the use of quotation marks or hyphens does not depend on the length of an adjective phrase. Instead, hyphens are used to join two or more words serving as a single modifier before a noun, whereas quotation marks are used for titles of shorter works or for indicating speech. For example, an adjective phrase with hyphens could be 'a well-known author,' regardless of length.
Emphasis can also be added using dashes; however, this again does not depend on the length of the phrase. Dashes are used to set off or emphasize content and are not specifically linked to the number of words in an adjective phrase. When quoting material, ellipsis points are used to indicate omitted words, while brackets indicate changes or additions to the original text.