Which is the best example of a secondary source document useful in the study of history?

In ohio in 1872, the cleveland massacre was a violent labor dispute at standard oil refineries in cleveland. a takeover by standard oil of the refineries in cleveland. an attempt to stop standard oil from becoming a monopoly. a failed attempt by standard oil to take over other refineries.

Why might the spanish government have approved of the encomienda system? a the system allowed for fair treatment of all under it, leading to a happy and prosperous colony. b the system used natives as slaves which meant the government was able to maximize their profit of exported goods. c the system allowed for mostly profitable trade within the different colonies. d the system was a great example of how to successfully run a colony, making spain a world power.

Demographers can compare a choropleth map to a to understand how geography influences population distribution and there are no a,b,c,or d u have to find it out ur self asap