Explain how blood cell formation is regulated using negative feedback mechanism

Ithink the answer is b

If your options are: a.climateb.nutritionc.povertyd.agethen your answer is letter a.if your options are a. food washing b. climate c. age d. poverty then your answer is also a.

Of that are from eating black  foods or iron supplements. the most common condition causing  it is a bleeding ulcer.  black poop caused by blood indicate a problem in the upper digestive tract.     along with pain, vomiting, or diarrhea is cause to see a doctor right go see a doctor