At the height of the Great Depression, it was said that about 25% of the labor force was out of work.
The factors that made it difficult for Eastern Europe to improve its water quality were outdated sewer systems, raw water quality, worn-out water utilities and unskilled employees. So we can say that four options given in the question fits the bill perfectly. These basic infrastructural reasons were responsible for being a hurdle towards improving the water quality. <span />
The answer is "t<span>he confederation among the states was too strong and too centralized" as this statement is not true so it can not be a disadvantage. </span>
Out of all those awnsers 6000 BCE is right.
