Welcher Stimmzettel wäre bei einer Bundestagswahl gültig?

Why this is the correct answer

On a German federal ballot (Stimmzettel), the first vote (Erststimme) appears on the left side and is cast for a specific candidate in your local constituency. This direct candidate vote determines which individual represents your district. Although the second vote (Zweitstimme) has a greater influence on the overall seat distribution, the first vote elects exactly one local representative per constituency.