In 2013, in Response to Their Frustration with Minority Filibusters

In 2013, in response to their frustration with minority filibusters, Senate Democrats decided to do which of the following?

A) Invoke "perpetual cloture" which ended the possibility of filibusters
B) Split appointments 50/50 among Republicans and Democrats
C) End legislative recesses until Republicans agreed to limit filibusters
D) Eliminate filibusters for confirmation of presidential nominees other than Supreme Court justices
E) Change Senate committee structures so that Republicans would be less represented and would lose influence