Explanation:

Assembling means buying necessary component parts and to fit them together to make a product. 'Assembly line' marks a production line made up of purely assembly functions.
It deals with what to buy, of what quality, how much from whom, when and at what price. People in business purchase to increase sales or to decrease costs. Purchasing agents are much tempted by quality, service and price. The products that the retailers buy for resale are selected as per the requirements and preferences of their customers.

Assembling means buying necessary component parts and to fit them together to make a product. ‘Assembly line’ marks a production line made up of purely assembly functions. The assembly operation includes the arrival of individual component parts at the work place and issuing of these parts for assembling.