What Most Likely Limited Research on Sexual Behavior Before the Late

What most likely limited research on sexual behavior before the late 19th century?

A) Biologists and sociologists lacked knowledge about reproductive anatomy.
B) Sex researchers were thought to be perverted, so they were not supported.
C) The available methods of research were not adequate for collecting data.
D) Media resources like the internet were not yet able to disseminate information.
E) Cultural and religious taboos kept researchers from pursuing sex studies.