When a problem is researched, authoritative sources should be used because they include thoughtful opinions.
are up to date.
are easy to find.
contain relevant information.

A or B i believe. You should define the word authoritative before picking a choice to determine which one it is. I would lean more to D

the protestant reformation's started in 1517, disturbing the religious and political order in europe´s catholic countries. the outcome was the european wars of religion prosecuted in europe in the 16th, 17th and part of the 18th century. nonetheless, uprisings, territorial disputes, and great power conflicts were also causes of the wars.  

answer: study

explanation:

maybe if you get off your phone and start studying you might do well but that’s your decision if you want to stay in summer school