What is the association of members of parliament from one party called in Germany?

EDITORIAL LEARNING AID

Why is this answer correct?

Members of parliament from the same party join together in a parliamentary group, which organises motions, speeches and committee seats. An association (a) is an interest organisation, the Council of Elders (b) is a body of the Bundestag, and opposition (d) refers to all the groups not in government.

Same party in parliament equals parliamentary group.

This translation and explanation are editorial learning aids. The official German wording and answer key govern the examination.