Three initial letters, three parts of a name.
C belongs to Christlich, D to Demokratische and U to Union. Matching these three words individually makes the correct answer clear among similar-sounding alternatives.
A party name is first of all a fixed designation. The abbreviation alone does not establish a specific legislative proposal or the behaviour of every member.

The other three answers
Check the exact words rather than just a similar sound.
Christian German Union
“Deutsche” incorrectly replaces “Demokratische” here. The name also begins with “Christlich”, not “Christliche”.
Club of German Entrepreneurs
CDU does not stand for Club Deutscher Unternehmer. That phrase expands the letters differently but is not the party name.
Christian German Environmental Protection
“Umweltschutz”, meaning environmental protection, is not the U in the name. U stands for “Union”.
CDU and CSU remain two parties.
The common form CDU/CSU refers to their joint Bundestag group, not one party with two interchangeable names. CSU has its own full name.
This vocabulary explanation is not a voting recommendation. The legal role of parties and their programmes are separate questions from spelling out the abbreviation.
Christian Democratic Union · CDU · Official name ↗C: Christlich. D: Demokratische. U: Union.
The German D means “democratic” here, not “German”.
Three words for this question
- die Abkürzungabbreviation
- A shortened written form of a longer name or expression.
- die Unionunion
- An association; here a fixed part of the party name.
- demokratischdemocratic
- Relating to democracy; here the middle word in the name.
