Step-by-step explanation:
FEV or Forced expiratory volume is the amount of the volume exhaled by the person during 1 second while VC refers to the maximal capacity of the exhaled volume after the maximal inspiration.
The FEV1 / VC ratio represents the maximal exhalation volume which depends on the age, weight and sex.
In the given case, the person is suffering from the restrictive lung disease which decreases the volume of the lung and therefore expansion of the lung. Since the expansion of the lung (inflation) is affected in this case but not the deflation therefore the person can exhale the air to its maximum limit.
Thus, the FEV1 / VC ratio remains normal.