Most gaseous pollutants come from a group of chemicals called

i think the answer is

mass

one would be wind another would be water density

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

the answer is otpion c) understanding

he wants to be heard one more time. he wants to be understood. he needs the truth one more time.