A.It is an economical way to process solid waste.
B.It is practical only for treating large amounts of solid waste.
C.It is not an efficient way to process solid waste.
D.It could reduce the cost of treating wastewater.
A.They have beneficial uses if contained.
B.They are destroyed in a later stage of APS processing.
C.They are both extracted during the first phase of APS digestion,
D.They are necessary to activate the anaerobic digestion process.
A.Studying for a test.
B.Visiting a close friend of theirs.
C.A class presentation they're preparing.
D.The television programme the man is watching.