Answer:

1.profitable, good, helpful, effective, convenient, fruitful, practical, appropriate, favorable, proper, pragmatic, suitable, handy, advantageous, utile, applied, brave, commodious, fit, functional.

2.Useful and harmful changes: Useful changes are also called desirable changes. Examples: The formation of curd from milk, and the decay of cow dung and leaves to form manure, etc,.

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