Historians compare similarities and differences between societies primarily to

to collect evidence on historical events.

Explanation:

Collecting evidence on historical events is one of the main works of historians. As historians recognize, it is in most cases difficult to find get accurate information about historical events from one source.

For example, information about the famous Titanic ship that collapsed on April 15, 1912, were accurately gathered from eyewitnesses account and were then compared to find similarities and differences before arriving at a true story of what happened in history.

add law

explanation:

the answer is d. tariffs were raised by america's trading partners after the smoot-hawley tariff act, decreasing exports, and declining job rates.