Main inspiratory muscle is -

Ans. is 'd' i.e., Diaphragm Respiratory musclesInspiratory muscles1. During quiet breathing : Diaphragm (most important), external intercostal and interchondral part of internal intercostal.2. During forced inspiration : Sternocleidomastoid, serratus anterior, serratus posterior superior, pectoral is major and minor, erector spinae, scaleni and levator costarum.Expiratory' muscles1. During quiet breathing : Passive process due to passive recoil of the lungs and thoracic wall.2. During forced expiration : Internal intercostal, innermost intercostal, transversus thoracis, serratus posterior inferior, subcostalis, lattissimus dorsi and abdominal muscles (rectus abdominis, internal and external oblique and transversus abdominis).