Why is it a good idea to have a carbon monoxide detector in the home?
to keep parents and children from suffocating
to avoid poisoning by a buildup of co gas
to warn members of the household of smoke from a fire
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It is a good idea because it helps to detect if there is too much carbon monoxide in the house. If there is too much, it can be poisonous and the detector will let you know. this answer would be TO AVOID POISONING BY A BUILDUP OF CO GAS. 
btw, is this platoweb? just curious.

Subtract your 2-minute  heart rate  from the  heart rate you took immediately after exercising. the faster your heart rate  recovers the fitter and healthier your  heart. 

during longer space exploration trips, crewmembers may develop vision impairment risks and short-term cardiac atrophy or a decrease in the size, strength, weight, and activity of the heart during space flight because they can experience microgravity. in addition, the long-term medical condition is loss of bone mineral density and radiation exposure.