6. . It is a useful change in materials to one's environment.
A. Burning of old tire.
C. Throwing of garbage in the canal.
B. Cutting of trees.
D. Cutting of fabric to be made into clothes.
7. It is a harmful change in materials to one's environment.
A. Cutting of fabric to be made into clothes.
C. Plastic bottle can used as flowerpots
B. Burning of garbage
D. Old tire can used as chair or plant pots.
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