The correct option is A Proportional representation
Elections to the Rajya Sabha, the Upper House of the Parliament, Vidhan Parishads, Upper Houses of the State Legislatures (existing only in a few states) and offices of the President and Vice-President are, however, conducted on the basis of proportional representation through a single transferable vote system. Hence, Option A is correct. The rest of the systems are not applicable to these elections, hence, incorrect.