The civilian conservation corps helped Americans during the great depression by working on projects with environmental benefits.<span />
Pandemics, diseases which spread to most populated regions with a high degree of mortality, have been recorded several times in world history, the first being the Plague of Justinian in 541 CE. The Black Death, also known as the Second Pandemic, was one of the most catastrophic events in human history.
The talk test is a simple way to measure relative intensity. In general, if you're doing moderate-intensity activity you can talk, but not sing, during the activity. If you're doing vigorous-intensity activity, you will not be able to say more than a few words without pausing for a breath.
Nutrient-dense foods are rich in nutrients relative to their calorie content. These include various healthy foods such as whole vegetables, fruits, cocoa, seafood, eggs and liver.