Why are biogeochemical cycles important?
1.
a) remains constant
b) can increase
c) can decrease
2.
a) destroy
b) create
c) renew

1. A) Remains Constant

2. C) Renew

Explanation:

Since it mentions how Earth is a closed system, materials will remain constant. They will not increase or decrease naturally.

So, knowing this, then we know that it's important that everything renews within the subsystems (similar to ecosystems). Knowing that materials will not necessarily increase or decrease, then we know they cannot be created or destroyed, as much as they can be renewed within the natural systems.