Question

(2) We must observe economy in the use of materials. ​

Answer 1

Answer:

We must observe economy in the use of materials because they directly or indirectly affect our environment. ... Increased use of man made materials pose a threat to the environment because their disposal is not easy and leads to environmental pollution.

Explanation:

HOPE IT IS HELPFUL.

Answer 2

Answer:

We must observe economy in the use of materials because they directly or indirectly affect our environment. Increased use of man made materials pose a threat to the environment because their disposal is not easy and leads to environmental pollution.