Which of the following is a brass musical instrument?

The Wagner tuba is an infrequently-used brass instrument that combines tonal elements of both the French horn and the trombone. Wagner was inspired to invent the Wagner tuba after a brief visit to Paris in 1853. He visited the shop of Adolphe Sax, the inventor of the saxophone and saxhorn. The term "Wagner tuba" has been used in English since the 19th century and is standard today.

The Wagner tuba was originally created for Richard Wagner's operatic cycle "Der Ring des Nibelungen". Since then, other composers have written for it, most notably Anton Bruckner, in whose Symphony No. 7 a quartet of them is first heard in the slow movement in memory of Wagner, and Richard Strauss, who composed several works that used the Wagner tuba, including his Alpine Symphony.