C. This is because when we need to breathe in the ribcage moves up and outwards and diaphragm moves down. This movement increases the pressure outside as compared to inside and air rushes in. During exhalation the ribcage moves down and the diaphragm moves upwards. This increases the pressure inside the body as compared to the lower pressure outside and the air is pumped out of the body.
THE ASWER IS TECNICALLY (C) BUT THE QUESTION IS WRONG. IN THE NSO WORKBOOK THE QUESTION IS ASKED FOR THE MOVEMENT OF RIBCAGE AND DIAPRAGM WHEN WE BREATHE IN AIR. THIS IS A TECHINAL ERROR IN SOFOLYMPIAD TRAINER.