Ice age. It caused saber tooth and mammoth to die
I would believe it is the Ozone but since it’s not an option the Ferrel Cell is the westerlies and the polar cell is the polar easterlies. So, I would say go with 4! Hope this helps, goodluck! xoxo.
The <u><em>correct answer</em></u> is:
He needs to select a more representative sample.
Explanation:
Choosing students from the basketball team for the sample he uses on a study of heart rates and exercise will be a biased sample. This is because students on the basketball team are potentially healthier than other students, which means that exercise will not have a large an effect on their heart rate as it would if they were not as healthy and not as physically fit.
In order to reduce the amount of bias, he should choose students from different groups throughout the school.
