What made Barack Obama’s election to the presidency in 2008 historically significant? Obama was the first president to ask for “hope and change.”

Obama chose a female vice-presidential candidate.

Obama was the nation’s first African-American president.

Obama offered an innovative solution to the Great Recession.

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