Many endurance athletes train at high altitudes before a major sporting event. They do this because they think that training at high altitude changes the number of red blood cells in their body.

Describe an investigation to find out if training at high altitude
does change the number of red blood cells in the human body.
(What are the control variables?)

In the united states there are strict fishing seasons and limits, but not all countries enforce similar laws. in bangladesh there are few if any fishing restrictions. what might be the reason for less restrictions in smaller countries like bangladesh? a) the united states is the only country worried about overfishing. b) the united states wants to limit the supply of fish to increase the price. c) bangladesh and smaller countries have an unlimited supply of fish in their coastal waters. d) small countries, such as bangladesh, are practicing subsistence fishing, taking only the fish needed to survive.