My elder brother got a motor bike but I ____ .

The sentence “My elder brother got a motor bike but I ____” requires “have not” to maintain parallel tense and convey that the speaker currently does not possess a motorbike. The past tense “got” suggests a completed action, and “have not” (present perfect) indicates the speaker’s current state. Options B (past tense, implying a specific event), C (future tense, irrelevant), and D (present continuous, incorrect structure) do not align with the sentence’s meaning, making A correct.