Answer:
The answer is C.
Explanation:
When answering to this type of question, it is always helpful to identify parts of the sentence. Father (our father) is performing the action, which makes him the subject of the sentence. Bought describes which action is performed, which makes it the predicate. Bycicles (new bycicles) are the direct object; they denote upon what the action is performed. And finally, my sister and me is the indirect object; they refee to someone affected by the performed action.
When pronouns are playing a role of a subject, they are written in nominative, basic form of a personal pronoun (I, you, he, she, it, we, you, they). However, if a pronoun plays a role of an object, direct or indirect, they are used as a object pronoun (me, you, him, her, it, us, you, them). That means:
I found this book.
The book is found by me.
Since here, the pronoun should be used as an indirect object, the correct answer is me.
