Which of the following changes (1- 4) usually tend to occur in the plain dwellers when they move to high altitude (3,500 m or more) ? (1) increase in red blood cell size (2) increase in red blood cell production (3) increased in breathing rate (4) increase in thromobocyte count changes occuring are a)(2)and(3) b)(3)and(4) c)(1)and(4) d)(1)and(2)