Differentiate primary from secondary suewage treatmen​

Primary Wastewater TreatmentSecondary Wastewater Treatment

In this method, the waste is processed through a physical procedure with equipment and filtration.The wastewater is purified through biological processes using microorganisms

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).