The death of Charles I was significant because A. he died without an heir.
B. England became a democracy.
C. he was tried and executed under the law.
D. no one had ever killed a reigning monarch before

C

Explanation:

a historian researching the immigration policies of the early 1900s would expect a source written today,rather than in 1910 to :

( a ) be more interested in objective data and statistics.

the answer to your question is:

strong-mayor system