Which Two Political Parties Are Causing All of Germany's Parties

Which two political parties are causing all of Germany's parties to begin engaging in grass-roots efforts to mobilize support from their rank-and-file members?

A) The German People' s Union and the Left Party
B) The Christian Democrats and the Greens
C) The Greens and the Left Party
D) The Social Democratic Party and the Free Democratic Party
E) The Communist Party and the National Democratic Party