Help for test pls help

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

Who did the first work in creating vaccines

Do all accounts serve the same function? why or why not? yes, all accounts people increase their money no, some accounts are for saving and others are for investing yes, all accounts are designed to ensure a retum on investment no accounts serve the purpose that their owners choose