Help me please someone help me 20 points please

Why did river valleys most farming impact the lives of neolithic peoples?

Why do you think the delegates to the first contintal congress believed that refusing to buy british goods would their cause?

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