Final answer:
To substitute a pronoun for 'Mary' in the sentence 'Mary cleaned the house', one would use 'she', resulting in 'She cleaned the house.' This maintains clarity while following the grammatical rules for pronoun case.
Step-by-step explanation:
Pronoun substitution involves replacing a noun or a noun phrase with a corresponding pronoun. In the sentence 'Mary cleaned the house', 'Mary' can be substituted by the pronoun 'she', resulting in 'She cleaned the house.' When using pronouns, it's important to select the appropriate case based on the grammatical function of that pronoun in the sentence.
Subjective case pronouns function as subjects, like 'I', 'we', and 'they'. Objective case pronouns function as objects, including words like 'me', 'us', and 'them'. In addition, when we encounter cases like comparison structures, careful attention is needed to choose the correct pronoun, as in 'Antonio cares more about having a clean kitchen than I [do]' or when questioning 'Who or Whom.'
Pronoun reference ensures that a pronoun clearly refers to its antecedent, the noun it replaces. For readability and precision, it's essential that pronouns do not create ambiguity in reference to their antecedents.