What do you think was the most pressing social issue facing the nation in the post-civil war era (1865-1910?

Need on these last 2 questions on my social studies homework 5 and 6 then i’m done with the homework

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

The three estates social system in france ensured balanced representation of all people and treated each social group fairly. true or false ? why?