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").

[EX Q]: Fact1: a fire requires oxygen to burn, Fact2: In the vacuum of space, there's no oxygen to burn., Question: Where is fire impossible? (A) evaporation (B) In space (C) A computer (D) uncontrolled (E) Inside a car (F) On television (G) summer end (H) On a mountain
[EX A]: B

[EX Q]: Fact1: Differentiation is the process by which unspecialized cells become specialized., Fact2: T helper cells differentiate to Memory cells and effector cells., Question: memory cells and effector cells are what compared to T helper cells (A) dermal & vascular tissue (B) antibodies (C) fetal development (D) antigens (E) occurs over a wide range (F) prokaryotic cells (G) unicellular organisms (H) more specialized
[EX A]: H

[EX Q]: Fact1: webbed feet are used for moving faster through water by aquatic animals, Fact2: Feet are webbed and serve as a rudder., Question: What are used as a rudder by aquatic animals? (A) dorsal (B) squids (C) feet (D) fibers (E) Tail (F) sharks (G) gills (H) clams
[EX A]:
C