In the late 1800s, many Russian Jews immigrated to the US to escape mistreatment in their native country. This is an example of a 
 A. push factor, because people left Russia to escape dangerous conditions.
 B. push factor, because people moved to the US for a specific opportunity.
 C. pull factor, because people left Russia to escape dangerous conditions.
 D. pull factor, because people moved to the US for a specific opportunity.