Washing soda can be used in
laundry
manufacture of glass & NaOH
textile and petroleum refinery
All of these
As we learnt ,
Uses of Na2CO3 -
1. In Laundry
2. In manufacture of glass, caustic soda etc
3. In textile and petroleum refinery
Thus, Na2CO3 can be used for all of the given options .
Therefore, option(4) is correct.