HELP! Indoor plumbing, medical advance, and improved personal hygiene practices have ___ human life expectancy.​

Chemistry worksheet - i am not sure what they are asking for exactly?

What causes different colors to appear in the sky? the absorption of light by air molecules the reflection of light by bodies of water the greenhouse effect in earth's atmosphere the scattering and reflection of light by dust particles

Which symbol can be used to indicate the pressure at which a chemical reaction is carried out? 25°c 2 atm pa