The option will be 5 .Here is the explaination.
Let X and Y be the No of Black and white balls in the Box.
Now There could be 3 possibilities . Below table presents Possibilities and changes happend due to the each outcome.
|| WW |
|| X+1,Y-2 |
Now here Y=2000 . X=731.If 3rd possibility happens all the time(WW) then There will be no white ball left in the Box beacuse 2|2000.So option 2 will be eliminated.
Again if other two possibilty happens then white ball will be as it is and no Black ball will be left.So option 3 is eliminated.
There is possibilty that the box may be empty beacuse y is decresing in 3rd possibility and x is decreaing in other two possibility but it may not be the case. so option 4 also eliminated.
So Option 5 will be the answer.
Correct me if i am wrong here.