A 65-year-old patient with COPD and a smoking history of 40 pack-years attends the clinic for routine review. His last spirometry six months ago showed an FEV1/FVC ratio of 0.60. What is the main criterion confirming a diagnosis of COPD?AReversible airflow obstruction with bronchodilatorsBFEV1 improvement of 15% after bronchodilatorCFEV1/FVC ratio <0.70 post-bronchodilatorDAbnormal chest X-ray showing hyperinflationESymptoms improving significantly with steroidsCheck my answer