(𝒊)To hear the sound of the coming train because sound travel within the rail track and get the idea of distance of incoming train.
(𝒊𝒊) Copper.
(𝒊𝒊𝒊) For safety as he cares for his friend..
(𝒊)To hear the sound of the coming train because sound travel within the rail track and get the idea of distance of incoming train.
(𝒊𝒊) Copper.
(𝒊𝒊𝒊) For safety as he cares for his friend..