Explanation

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'

'po sur kop' means 'cards and tennis'

In first the three sentences the code 'ki' is common and word 'playing' is common. So, 'ki' means 'playing'.

In first two sentences the code 'ki ma' and word 'is playing' is common. So, 'ma' means 'is'.

In first and fourth statement the code 'po' and the word 'cards' is common. So, 'po' means 'cards'.

In second and fourth the code 'kop' and the word 'tennis' is common. So, 'kop' means 'tennis'.

From statement 2, 'ja' means 'Ahsa'.