Which two of the following changes (a – d) usually tend to occur in the plain dwellers when they move to high altitudes (3,500 m or more)?
 

Changes occurring are:
1. (b) and (c)
2. (c) and (d)
3. (a) and (d)
4. (a) and (b)

Increased asthmatic attacks in certain seasons are related to:

1. hot and humid environment

2. eating fruits preserved in tin containers

3. inhalation of seasonal pollen

4. low-temperature