There are many important reasons why populations of highly developed countries decline. To number some, easy access to contraceptive method together with the a high level of female education makes birth control one important factor on population downward. Moreover, a stable economy improves lifestyle helping the population to choose professional careers thus focusing on different aspects but not making children.
On the other hand, it is important to mention that although the population in developed countries might be declining, the death rate is declining as well. As above mentioned, the lifestyle can be high and the aspects as shelter and a living space makes people healthier. Along with the economical growth comes the technological and health care advancement which greatly help the population of the developed countries to have easier and more affordable access to medical treatment making date rates lower.
OK! so i just did this question not too long ago after studying it my answer was "C"
I think its water and iron
