primary outcome primary outcome measure primary outcomes primary output primary ovarian primary packaging primary part primary particle primary particles primary partition primary partitions primary partner primary parts primary path primary phase primary phone primary physician primary piston primary place primary point primary point of contact primary position primary power primary power supply primary prevention primary principles primary problem primary problems primary process primary processing primary producer primary producers primary product primary production primary productivity primary products primary program primary progressive primary protagonist primary protein primary provider primary public primary pump primary purpose primary purposes primary question primary race primary radar primary raw primary reaction primary reactor primary reason primary reasons primary reference primary relationship primary requirement primary requirements primary research primary research interests primary reserve primary residence primary residences primary resource primary resources primary response primary responsibilities primary responsibility primary results primary risk primary road primary roads primary role primary roles primary root primary route primary rule primary rules primary safety primary school primary school age primary school attendance primary school children primary school completion primary school education primary school enrolment primary school for girls primary school has primary school is located primary school level primary school pupils primary school student primary school students primary school teacher primary school teachers primary schools primary schools have primary science primary screen primary screening