Answer: alternative D.
Explanation: Dr. DeVries should choose his sample population randomly in order for his research to be representative, even having a specific population, which is high school seniors, that he wants to study. By <u>choosing specifically students from an exclusive college preparatory school, he isn't considering how students from other schools might perform in his research test</u>. This would be a very important step for him to understand how the practice in problem solving affects the ability related to it. Otherwise, he will have a distorted result.
Mayan number system is a vigesimal system- that means with a base of 20:
the correct answer is: 20, the Mayan number system is based on the number 20.
This means that a number like 360 is expressed with "18 times 20".
Scientists suggest that number systems based on 10 are inspired by the number of fingers, and number systems based on 20 could be based on fingers counted twice: after the number 10, hands would be turned upside-down.
Just as other peoples' feelings can affect the message they're trying to send, your own feelings can get in the way of your communication as well. When you feel a strong emotion or feeling, pay attention to that emotion and try not to let it get in the way of your message
