In a certain code language, if 'sky' is known as 'earth', 'earth' is known as 'water', 'water' is known as 'air', 'air' is known as 'light', and 'light' is known as 'sound', then what is it that humans breathe in?

Light

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 A   B   C    D   E    F   G    H    I    J    K    L   M

 ↓    ↓    ↓    ↓    ↓     ↓   ↓    ↓     ↓   ↓    ↓    ↓    ↓

 Z   Y    X   W   V    U   T    S    R   Q   P    O   N

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THE LOGIC FOLLOWED HERE IS:

WORD                 IS CALLED

SKY                        EARTH

EARTH                    WATER

WATER                      AIR 

AIR                          LIGHT

LIGHT                      SOUND

SO HUMANS BREATH IN AIR

AND AIR IS CALLED LIGHT

SO LIGHT IS CORRECT ANSWER