-6+1= -5
-5 is the true answer
Copper is a heavy metal that can harm many people. This process of heavy metals building in your body is called bioaccumulation and the process of this building in the food chain is called biomagnification. Its hard to rid of this heavy metal because it is very dense, therefore, cannot breakdown in our bodies. Heavy metals get consumed by producers and then reach to the top of the pyramid (us) so we have the highest risk of getting diseases and so on. Make sure you explain that heavy metals get passed from industrial purposes where companies do not dispose of waste properly.
Source: Exam as well
Good luck!
The first one is 2
The second is 1
The third is 6
And the fourth is 3
That point is called as EQUILIBRIUM, and then you have to note that value to compare with others