Which of these is correct with reference to a composite pit?​

d) All of the above.

Explanation:

Composite pits are used to make fertilizer when biodegradable material is put inside the pit so that it can decay. The biodegradable refuse is placed with soil and then occasionally sprinkled with water.

When it decays, the product can be a source of very useful fertilizer. As this is naturally made, it reduces pollution of soil and water resources.  

the answer is crop rotation

(4,-2)

explanation:

6x+4y=16

-6x-9y=-6

-5y=10

y=-2

x=4