What two key conditions led to the birth of civilizations?

What was the purpose of the federal reserve act

Which nonverbal cue most likely indicates that a person is open to a conversation? lack of eye contact crossed arms smiling mouth o monotone voice

Ascientist performs an experiment where she measures the mass of a piece of metal, pours acid onto the metal, washes the metal, and then re-measures the mass of the metal. the scientist repeats the experiment several times, each time increasing the amount of acid used. the dependent variable in the experiment is the: initial mass of the metal final mass of the metal amount of acid used washing the metal