Final answer:
The correct pronoun to complete the sentence is 'he', as it follows a linking verb and should be in the subjective case. The English language traditionally uses 'he' for masculine and 'she' for feminine, but it is evolving to include gender-neutral pronouns like 'they' for inclusivity.
Step-by-step explanation:
To complete the sentence correctly, the word that should be used is 'he'. This is because when a pronoun follows a linking verb, such as 'is', the subjective case 'he' should be used rather than the objective case 'him'. Therefore, the sentence should read, "Don’t you think Nancy is as smart as he?"
In choosing pronouns, it's essential to consider their case, singular or plural form, and whether they reflect gender neutrality, when necessary. The use of 'he' and 'she' are traditional ways to address gender, but the English language is evolving to include gender-neutral terms like 'they' to promote inclusivity. Each pronoun has its counterpart, and the context will help determine the correct form to use.