Which of the following are the right bank tributaries to Ganga?

The major right bank tributaries that flow directly into the Ganga River are the Yamuna and the Son. While the Chambal flows into the Yamuna, and the Damodar flows into the Hooghly, the most appropriate direct right-bank pair combining with direct or sub-basin systems from the standard choices is option B, as both Yamuna and Son join Ganga directly from the right south side, and Damodar joins its distributary. Let's note that Gandak is a left-bank tributary. Therefore, options containing Gandak are ruled out, making B or A common alternatives. Since Son and Yamuna join Ganga directly, B fits perfectly in historical questions.