Topic: Conditional Sentence,

Best Answer Explained in Below-:

The sentence "If your sister --- , she would come." is structured as a conditional sentence, which expresses a hypothetical situation. In English grammar, the type of conditional used here is known as the second conditional, which is used to talk about unreal or unlikely situations.

In second conditional sentences, the structure typically follows the format: "If + subject + past simple verb, subject + would + base form of the verb." Here, the correct form to fill the blank is "were invited" (option D), which correctly uses the past subjunctive form "were" for hypothetical situations, regardless of the subject.

The other options—"invited" (A), "invites" (B), and "inviting" (C)—do not fit the structure of the second conditional. "Invited" could suggest a completed action, "invites" is present simple, and "inviting" is a gerund or participle form, none of which convey the intended hypothetical nature of the situation.

Therefore, "If your sister were invited, she would come." implies that her coming is contingent upon the condition of her being invited, highlighting the unreal aspect of the situation.