Afghan refugees living in Iran to escape terrorism - Push factor
Bangladeshi migration to India due to flood - Push factor
Admission to university in England - Pull factor
Migration to Canada for a better lifestyle - Pull factor
Migration to America to escape religious persecution - Push factor
Entrepreneur moving to Singapore for a better business opportunity - pull factor
I believe it is the outer crust but i will do more reaserch for you :)
You might be looking for "parliament"
Density (a) is the correct answer
<span>Scientists believe that differences in density cause hot, plastic-like rock in the asthenosphere to rise toward earth's surface. </span>