Answer the following question: Extract the answer to the question from the following context. Question: Which symptom of the condition in which a person's airways become inexplicably inflamed and produce mucus involves difficulty taking in and expelling air? Context: Asthma is characterized by recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. Sputum may be produced from the lung by coughing but is often hard to bring up. During recovery from an attack, it may appear pus-like due to high levels of white blood cells called eosinophils. Symptoms are usually worse at night and in the early morning or in response to exercise or cold air. Some people with asthma rarely experience symptoms, usually in response to triggers, whereas others may have marked and persistent symptoms.
Answer:
shortness of breath