Is returning to an earlier time (in a story) for the purpose of making something in the present more clear

Explain how you might determine the rate of weathering on a sample rock

Nathan is an ecologist. he’s studying the effect of secondary consumers on primary consumers. his current research focuses on a population of blue jays and crows. they eat caterpillars and mice. if the number of blue jays increases, what are the likely effects on other populations? 1the number of crows will increase. 2the number of mice will decrease. 3the number of mice will remain the same. 4the number of caterpillars will decrease.

Carbon dioxide can be produced form what type of power generation?