Question

After being promoted to higher class, pawan sells his old books to a second- hand bookshop. is it a business activity why

Answer 1

No this is not a business activity.

A business is that activity which is done regularly and frequently with the primary objective of earning profit

Even if a business which for example sells computers, decided to sell off old and used furniture, it won't be included under the head profit from business activity, It will be included in income from other sources.
I.e it won't be considered a business activity.

The fact that pawan has sold his second hand book after personal use does not make it a business.
It is not done regularly.
It is not done frequently.
And although pawan gained some revenue, whether it was sold in profit or loss is in question.