What kinds of evidence do historians use to study the past?

Acustomer uses goods and services to ?

During the cold war, which of the following groups of countries would have all been"behind the iron curtain"

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