Why do cats purr when they are happy?

How many atoms of oxygen are contained in 160 grams of n2o3

Which statement is a reason to support population regulation? a) it is unethical for us to control birth control rates b) humans have the freedom to produce as many children as desired c) the gap between the rich and poor has been narrowing since 1960 d) billions more people on the earth will intensify many environmental and social problems

Stage in which a typical star has completely stopped fusion