The way that scientist determine when an era begins and when it ends is : Mass extinction of an organism
For example, millions years ago, the world was under the era of dinosaurs, which were simply the most superior beings on earth during that time, after they became extinct, the earth enter the era of the mammals
Answer:
Factory workers put in very long hours for six days a week.
Explanation:
In a prominent model of self-administration developed by George Koob, rats are allowed to self-administer cocaine for either 1 hour each day (short access) or 6 hours each day (long access).
