Arrange the following activities in a sequential order according to their occurrence.

(a) Vertical shafts

(b) Underground galleries

(c) Underground mining

(d) Transport to the surface

Choose the most appropriate answer from the options given below:

(a), (b), (c), (d)

When the ore lies deep below the surface, underground mining method (shaft method) has to be used. In this method, vertical shafts have to be sunk, from where underground galleries radiate to reach the minerals. Minerals are extracted and transported to the surface through these passages. It requires specially designed lifts, drills, haulage vehicles, ventilation system for safety and efficient movement of people and material. This method is risky. Poisonous gases, fires, floods and caving in lead to fatal accidents.