Read this and answer the question. If the question is unanswerable, say "unanswerable".

The Classical era stringed instruments were the four instruments which form the string section of the orchestra: the violin, viola, cello and contrabass. Woodwinds included the basset clarinet, basset horn, clarinette d'amour, the Classical clarinet, the chalumeau, the flute, oboe and bassoon. Keyboard instruments included the clavichord and the fortepiano. While the harpsichord was still used in basso continuo accompaniment in the 1750s and 1760s, it fell out of use in the end of the century. Brass instruments included the buccin, the ophicleide (a serpent replacement which was the precursor of tuba) and the natural horn.

What instrument was the precursor of the tuba?
the ophicleide