Final answer:
The phrase 'had not been invented yet' is a fragment, not a complete subject. Fragments lack essential components like a main subject and verb. To correct a fragment, it can be attached to a complete sentence or rewritten to include the necessary elements.
Step-by-step explanation:
The phrase 'had not been invented yet' is not a complete subject; it is a fragment. In English, a complete subject must have a main noun (or pronoun) along with all of its modifiers. A fragment, on the other hand, is missing essential components that make it a complete sentence. Fragments often occur when they follow a complete sentence and expand on it without forming a complete thought by themselves. To avoid fragments, one can attach the fragment to a complete sentence or rewrite it to include a main subject and a verb. For example:
- Unintentional Fragment: 'had the official maps of the United States tinkered with.' This lacks a main subject and verb.
- Complete Sentence: 'My father had the official maps of the United States tinkered with to hide our location.'
In the second example, the phrase becomes part of a complete sentence because it includes a main subject ('My father') and a main verb ('had tinkered with').
Recognizing and correcting sentence fragments is an important part of subject/verb agreement and constructing coherent sentences. As illustrated in section 13.2 of a grammar guide, ensuring the subject and verb agree in number and person is essential for creating correct and understandable sentences.