garbage decomposes in a landfill and gives off methane gas. what kind of change is this? *

physical change
chemical change
partial change
extensive change

the answer to this question is 3.

what is the question?

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.