In Which of the Following Ways Does the Electoral Structure

In which of the following ways does the electoral structure under Putin differ from that under President Yeltsin?

A) It has two rounds of voting for the Duma instead of a single round.
B) It is pure proportional representation instead of mixed PR and SMD.
C) Voters must cast ballots for individual candidates instead of for parties.
D) Voters must demonstrate registration with a specific pre-approved political party in order to cast a ballot.