You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "where is the mouth of the danube river located?" whose answer is Danube Delta.
Each document should contain about 30 words, and these documents should contain useful information.

Query: location of the mouth of the danube river
Useful Output:

Doc 1: It rises in the Black Forest mountains of western Germany and flows for some 1,770 miles (2,850 km) to its mouth on the Black Sea. Along its
Doc 2: The Danube forms on the Western slopes of the Black Forest in southwest Germany. It starts life at the confluence of two streams – Brigach and
Doc 3: From source to mouth. The Danube has its source in the Black. Forest in Germany, and flows over. 2800 km to its mouth in the Black Sea.
Doc 4: Did you know that the Danube originates in Germany and that it flows into the Black Sea in Romania? On its way from its source to its mouth,
Doc 5: Mouth · Danube Delta. - location, Ukraine. - coordinates, 45°13′3