From which country did the first guest workers come to the Federal Republic of Germany?

EDITORIAL LEARNING AID

Why is this answer correct?

The Federal Republic of Germany concluded its first recruitment agreement with Italy in 1955; the first guest workers therefore came from Italy. Spain (b) and Portugal (c) followed in 1960 and 1964 respectively, Turkey (d) in 1961.

First recruitment agreement in 1955 with Italy – Italians came first.

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