Factors that would serve as a stimuli for erythropoiesis?

Question

What factors would serve as stimuli for erythropoiesis?

1. Hemorrhage
2. Aerobic exercise
3. Living at a high altitude
4. Breathing pure oxygen

Would it be 3 and 4? Thanks for the help.

Answer 1

it wud b 1. fer sure..though im confused bout 3. since erythropoiesis is a result of anoxia(lack of oxygen) which does happen at high altitudes..