A is representing diaphragm in the given diagram and it performs the following role:
(i) It helps to decrease the residual volume of air in lungs: True, during expiration, as the diaphragm and intercostal muscles relax, the lungs and thoracic tissues recoil, and the volume of the lungs decreases, this reduces the volume of the lungs and hence pressure within the lungs increases above that of the atmosphere. This results in expelling of the residual volume of gas remaining in the lungs.
(ii) It flattens as we exhale: True, diaphragm is dome shaped and flattens as we inhale and relaxes as we exhale.
(iii) It gets raised as we inhale: False, raising of diaphragm would lead to restricting the expansion of volume of lungs and hence pressure inside will decrease and thus will not accommodate oxygen.
(iv) It helps the chest cavity to become larger: True, by increasing the volume and decreasing the pressure inside.
Thus, the option which correctly matches with the role of diaphragm during breathing is (d) (i), (ii) and (iv).