Q: In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").
Fact1: Vertebrate chordates have a backbone., Fact2: Birds are a class of the chordates or vertebrate phylum., Question: what have a backbone? (A) carbon (B) toads (C) birds (D) cats (E) humans (F) bacteria (G) dogs (H) lungs
A:
C