I could be wrong but I think B, Although I would take someone other than my answer. Sorry i didn't know for sure.
Cyanobacteria, also known as "blue-green algae", are the unicellular organisms which are able to produce oxygen.
Approximately 540 years ago, the atmosphere was very poor on oxygen. Cyanobacteria are thought to be responsible for the oxidization of the atmosphere back then, in an event known as <em>"The Great Oxygenation Event"</em>. As a result, Earth's life forms suffered drastic changes in their composition, as they evolved from being <em>anaerobic</em> to becoming organisms <em>highly dependant</em> on oxygen. The oxygenation of the atmosphere would eventually provide the adequate environment in order for the <em>Cambrian Explosion</em>, or the first diversification of living organisms, to happen.
Answer:
The wall was built to prevent East Germans from fleeing and stop an economically disastrous migration of workers.
He was trying to deal with the East Germany's refugee problem which was The East Government was extremely unpopular-so many East Germans fled to West Germany- between 1949 and 1961 2.7 million escaped to West Germany- Many of these were very skilled- such as doctors.
To make this answer short The problems that Krushchev was trying to deal with was to keep the East Germans from fleeing and to stop an economically disastrous migration of workers.
Explanation:
They viewed reaching an advanced age as a significant accomplishment.
Life expectancy in early colonial Virginia was less than 25 years -- including the reality of infant mortality and a high number of deaths in childhood. In the colonial beginnings of New England, around 40% of children died before reaching adult age. Life in the colonies was very hard for the early colonists.
