Answer:
Conveyor belts.
Step-by-step explanation:
Conveyor belts are a never ending flexible belt which is moved by chain of rollers for carrying objects from one place to another. Conveyor belts is an important tool used in material industry for transporting materials in bulk from one place to another. The material handling industries use conveyor belts to move bulky products such as salt, grain, ore, etc from one place to another.
The inventory firms use conveyor belts to move delicate products from one place to another.
Therefore, conveyor belts is the correct answer.