Ramu decided to set . . . . . . . . some time everyday for prayers. A. aside B. up C. in D. on

The correct answer is A. aside.

To set aside something means to keep it for a particular purpose. In this case, Ramu is setting aside some time every day for prayers.

The other options do not make sense in this context. To set up something means to establish or arrange it. To set in something means to put it in a particular place or position. To set on something means to start or cause something to happen.