Why Did Durkheim's Contemporaries Overlook Social Forces as Possible Causes

Why did Durkheim's contemporaries overlook social forces as possible causes of suicide?

A) because suicide was rare
B) because instances of suicide were concealed and their numbers were unknown
C) because there can be no social reasons for carrying out such an individual act
D) because suicide was considered an individual act of desperation, often resulting from a psychological disorder