i think it is 1. trait 2.complex 3. system 4. region
The earth was formed at approximately 4.5 Billion BC
The correct answer is: Russia (although big parts of Russia are not in Eastern Europe but in Asia.
Russia has a huge territory which is generally very empty, especially in the North, where the conditions are harsh -there are only 150 million people in Russia, 10 million of which live in or near Moscow.
The "Census Tract" is an area roughly equivalent to a neighborhood established by the Bureau of Census for analyzing populations. They generally encompass a population between 2,500 to 8,000 people. Bureau of Census describes them as "relatively permanent", but they do change over time.