निम्नलिखित में से कौन सा संयोजन विश्व के चार प्रमुख उच्च घनत्व वाले जनसंख्या समूहों (clusters) का प्रतिनिधित्व करता है?

In traditional anthropological classification of human races, which racial group was characterized as 'yellow-skinned'?

What is the approximate estimated proportion of ecumene (habitable) and non-ecumene (uninhabitable/sparsely inhabited) areas on the Earth's surface?