Sorrow: Cry: Mirth: ?

Find the related words.
$$ {L\over S}:{12\over 19}::{I\over T}:?$$

Direction: In the following question, select the related word from the given alternatives. 

India : New Delhi :: Pakistan : ? 

Direction: In the following question, select the related word from the given alternatives. 

College : Dean :: Museum : ? 

Direction: In the following question, select the related word from the given alternatives. 

Train : Passenger :: Aeroplane  : ?

Choose the odd word/letters/number/number pair from the given alternatives. 

Den is to Lion as Aviary is to 

Bow is to Violin as Plectrum is to