Although iran is larger than turkey both countries have similar populations why might this be so?

Their proximity to each other have given them some similar topography; i.e. both countries posses considerable amount of mountains and are subject to frequent earthquakes, which have cost each country with substantial amount of deaths.  Similarly, both Turkey and Iran posses a diversity of climate conditions.  Even though Iran is twice as big as Turkey, the latter has slightly higher population.  While Turkey is one of the world’s few self-sufficient in basic food, Iran is among the world’s leaders in its reserves of oil and natural gas

81 is a composite number

A,b,c is the answer to the question