State three factors affecting breathing rate in human beings

age, smoking habits, and size/weight

Explanation:

The older you get, the weaker you'll be, so your breathing will be effected.

If you smoke then your lungs will be effected which will ultimately have an affect your breathing.

If you're really heavy (ex. Over weight) then you will get tired more easily, which will effect your breathing rate.

option a and d is the correct answer

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the real answer is b. scintillation counter