Detailed Instructions: 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").
Q: Fact1: a seismometer is used to measure the strength or magnitude of an earthquake, Fact2: Seismic waves are produced by earthquakes., Question: What does a seismometer do to seismic waves? (A) it increases (B) measures (C) stops (D) their speed (E) grounds (F) counterop (G) waves at (H) visibility
A:
B