You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Boston

Context:
Air quality in Boston is generally very good: during the ten-year period 2004–2013, there were only 4 days in which the air was unhealthy for the general public, according to the EPA.

Question:
How is the air quality in Boston?

generally very good