'Light' is related to 'Darkness' in the same way as 'Transparent' is related to '___________'.

"Light" = "Darkness"

"Transparent" = ?

Logic: The given analogy represents an opposite relationship (antonyms).

'Light' is the opposite of 'Darkness'.

Similarly,

'Transparent' (which allows light to pass through completely) is the opposite of 'Opaque' (which does not allow light to pass through).

Thus, the correct option is: (c) Opaque