This question tests your understanding of gerunds and pronoun case in English grammar.

Concept Explanation

The verb "approved of" is a phrasal verb that requires an object. This object must be a noun or a noun-like element. In this sentence, the action of "staying in England" is the object of the preposition "of".

When a verb acts as a noun (in this case, "staying"), it is called a gerund. A key rule is that when a pronoun comes before a gerund, it must be in the possessive case (her, his, my, your, their, our) and not the subjective case (she, he, I, you, they, we).

Therefore, the correct structure is: Possessive Pronoun + Gerund.

Let's apply this to the sentence: "Mary's father approved of her staying in England..."

• "her" is the possessive pronoun.
• "staying" is the gerund (the -ing form of the verb acting as a noun).

The other options are incorrect because:

• she to stay / her to stay: The infinitive "to stay" is not used as the object of the preposition "of" in this context. The structure "approve of someone to do something" is grammatically incorrect.
• she will stay: This introduces a future tense clause ("she will stay"), which cannot be the object of the preposition "of".

Related Topics & Theory

Gerunds: A gerund is a verb form ending in "-ing" that functions as a noun. It can be the subject, object, or object of a preposition in a sentence.

Pronoun Case: Pronouns change their form (case) based on their function in a sentence.

• Subjective Case (I, you, he, she, it, we, they): Used when the pronoun is the subject of a verb. (e.g., She stays in England.)
• Objective Case (me, you, him, her, it, us, them): Used when the pronoun is the object of a verb or preposition. (e.g., He approved of her.)
• Possessive Case (my, your, his, her, its, our, their): Used to show ownership or, crucially, before a gerund. (e.g., He approved of her staying.)

Final Answer

The most appropriate word to fill in the blank is her staying.

The complete sentence is: "Mary's father approved of her staying in England for another year in order to improve her English."