What is Sister-7 doing ?

Question

There are seven sister in a house in a village where there is no electricity or any gadget.

Sister-1: Reading Novel
Sister-2: Cooking
Sister-3: Playing Chess
Sister-4: Playing Sudoku
Sister-5: Washing clothes
Sister-6: Garderning

What is Sister-7 doing ?

Answer 1

Logically Sister-7 is playing chess with Sister-3

Answer 2

Playing chess

Answer 3

Sister-7 is playing chess with sister-3, because chess cant be played individually.