This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
In moderate severity obstructive lung disease, the expected abnormalities include the following except- 
Select and explain. 
A. (upward arrow) Residual capacity, B. (downward arrow) Vital capacity, C. (downward arrow)FRC/TLC ratio, D. FEV1/ IFVC<70%
C: (downward arrow)FRC/TLC ratio
Answer: C: (downward arrow)FRC/TLC ratio 
Explanation: In moderately severe obstructive lung diseases,FEV1/FVC ratio will be less than 0.7 and FEV1 will be 50-80% predicted.TLC will be increased,FRC is more severely elevated due to loss of lung elastic recoil & dynamic hyperinflation.RV is very severely elevated due to airway closure.Vital capacity will be decreased.So FRC/TLC will be increased in obstructive lung diseases. Reference:Harrison's Medicine-20TH edition