Which two statements about redox reactions are true.

Which two statements are true about a system? 1. a system is a group of objects analyzed as one unit. 2. energy that moves across system boundaries is conserved. 3. there’s only one way to define the boundaries of a system. 4. all systems are made by humans.

After rain, water soaks into the ground and is added to the groundwater. this process is known as a. groundwater pollution. b. groundwater recharge. c. groundwater recycling. d. groundwater filtration.

This graph represents four ecosystems. each ecosystem has a different number of species, adding to its biodiversity. different colors represent different species. which statements correctly summarize the data depicted by the graph? 1. ecosystem d has more biodiversity than ecosystem c. 2. ecosystem b has more biodiversity than all the other ecosystems. 3. ecosystem a has more biodiversity than ecosystem b but less biodiversity than ecosystem c. 4. ecosystem b has more biodiversity than ecosystems c and d but less biodiversity than ecosystem a. 5. ecosystem a has more biodiversity than ecosystem c but less biodiversity than ecosystem b.