<prompt> A patient presents with breathlessness. He has bilateral basal crepitations, lung function tests reveal a decrease in total lung capacity TLC and vital capacity VC with normal FEV1 FVC ratio. What is the most likely diagnosis?Chronic bronchitisIdiopathic pulmonary fibrosisCystic fibrosisAllergic bronchopulmonary aspergillosis  <response>: The presence of reduced TLC VC points to Restrictive pattern and is confirmed by normal FEV1FVC ratio. Cystic fibrosis Chronic Bronchitis leads to Obstructive airway disease. ABPA causes central bronchiectasis and is a suppurative lung disease. 