Why is it difficult for scientist to find fossils from the pre-Cambrian period

the genotypes would be 50% bb and 50% bb

the phenotypes would be 50% brown and 50% white. hope this : )

significant amounts of nitrogen oxides, carbon monoxide, and other pollution

explanation:

passenger vehicles are a major pollution contributor, producing significant amounts of nitrogen oxides, carbon monoxide, and other pollution. in 2013, transportation contributed more than half of the carbon monoxide and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into our air.