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?)

Doing their exercise at higher altitudes is right to improve their endurance

Explanation:

The reason is at high altitude there is reduction in the amount of oxygen which we need to take in for respiration.So by training at high altitude they are training their red blood cells to adoat to the fact of lower oxygen intake because when an athlete starts his job he uses only a smaller amount of oxygen so in order to win he trains himself(ENDURANCE)to last longer on tracks

the answers are a and c

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.