Breathing and Exchange of question bank (Zoology)

Two friends are eating together on a dining table. One of them suddenly starts coughing while swallowing some food. This coughing would have been due to improper movement of

Which two of the following changes $(1-4)$ usually tend to occur in the plain dwellers when they move to high altitudes $(3,500 \mathrm{~m}$ or more)? (A) Increase in red blood cell size (B) Increase in red blood cell production (C) Increased breathing rate (D) Increase in thrombocyte count Changes occurring are