In a certain language, 'po ki top ma' means 'Usha is playing cards' ;
'kop ja ki ma' means 'Asha is playing tennis' ;
'ki top sop ho' means 'they are playing football' ;
and 'po sur kop' means 'cards and tennis' ;
Which word in that language means 'Asha' ?
In the first and second statements, the common code words are 'ki' and 'ma' and the common words are 'is' and 'playing'.
So, 'ki' and 'ma' are the codes for 'is' and 'playing'.
In the second and fourth statements, the common code word is 'kop' and the common word is 'tennis'.
So, 'kop' stands for 'tennis'.
Thus, in the second statement, 'ja' stands for 'Asha'.