Gold. However they produce silver and nickel as well.
The answer is: C. Unlike fixed interval reinforcement schedules, with variable interval reinforcement schedules, the time between a behavior and the following consequences varies around a specified average.
When the researchers conduct a fixed interval reinforcement schedules , the reward for a certain behavior would be given after a specific amount of time has passed.
When they conduct variable interval reinforcement schedules, the reward will be given within unpredictable time frame. Because the reward time is unpredictable, there is no expectation between the subject after the subject did the desired behavior. This will make the time between a behavior and the following consequences varies around a specified average depending on the subject's characteristic.
The most populated place/country would be China with a population of 1.4 billion people
