Why do people only inhabit about 30% of the land on earth

In japan, the is the head of state and the is the head of government. who ever answer will get

It can be inferred that the dramatic increase in defense spending by germany was the result of. (a) attempts by great britain to take german colonies. ( b) fear of a two-front war against france and russia (c) the need to put down a communist rebellion (d) a competition with the allies to produce atomic weapons

Atsar was a russian leader in early 1900 who was similar to a?