Distinguish a federal state from a neighbouring country.
Saxony and Bavaria are German federal states. Their borders with Czechia also form parts of Germany’s national border. Czechia is therefore a neighbour of Germany even though the border runs through two German states.
“Czechia” and “Czech Republic” refer to the same country here. The existing English question bank uses “Czech Republic”. These are not two different neighbouring countries.
The other three answers
The other three choices share no national border with Germany.
Bulgaria
Bulgaria does not directly border Germany. A country can be part of Europe without being Germany’s direct neighbour.
Greece
Greece has no shared land border with Germany. The question asks for a direct neighbour, not a familiar European travel destination.
Portugal
Portugal is not one of the countries directly adjoining Germany. A transport or trade connection does not establish a shared border.
Borders between German states are different.
The border between Saxony and Bavaria separates two federal states within Germany. The border between either of them and Czechia separates two countries. The German word “Land” can refer to either level; context determines the meaning.
The question does not require an exact border length or the name of a crossing. The reliable reference is that Czechia is the country on the other side of Germany’s border in Saxony and Bavaria.
The border with the Czech Republic · Saxony State Surveying Authority ↗Saxony and Bavaria are on the German side; Czechia is the neighbouring country.
Two German federal states along a national border do not mean two different neighbouring countries.
Three words for this question
- die Staatsgrenzenational border
- The boundary between two countries.
- der Grenzabschnittborder section
- A particular part of a longer border.
- unmittelbar angrenzento border directly
- To share a border without another country in between.