What does corroborating sources allow a historian to do

Corroborating sources allow historians to prove their system of hypothesis, and to generalise about some events, because they found factual evidence to sustain their research. It's an important subject, because historians have the challenge to prove hypothesis that are based in social evidence that usually take place in the past.

it provided for selection of government employees through competitive examinations. it also made it unlawful to fire or demote covered employees for political reasons or to require them to give political service or payment, and it set up a civil service commission to enforce the law.

explanation:

she will pay the extra amount