The correct answer is: B. against
The English schemed to continue their rule in India by playing off one community against the other. This means that they tried to make the different communities in India fight each other, so that they would not be able to unite against the English.
Option A, “with,” is incorrect because the English did not want to work with the different communities in India. They wanted to keep them divided so that they could rule over them.
Option C, “upon,” is incorrect because the English did not want to force the different communities in India to do anything. They wanted to make them fight each other on their own.
Option D, “before,” is incorrect because the English did not want to wait for the different communities in India to unite against them. They wanted to keep them divided so that they could rule over them for as long as possible.