Question

form a compound sentence.
___________________________ the official language is german.
in austria, but not in poland,
in both germany and austria,
the capital of austria is vienna, and
in the european country of austria,

Explanation:

To form a compound sentence, we need two independent clauses joined appropriately. The option "The capital of Austria is Vienna, and" provides the first independent clause ("The capital of Austria is Vienna") and the conjunction "and" to connect to the second clause ("the official language is German"). The other options are phrases or do not form a proper compound sentence structure.

Answer:

The capital of Austria is Vienna, and