"¿Cuál es el largo de ese puente?"
Traducción:What is the length of that bridge?
How long is that bridge? I would like to know why that answer is wrong.
It's fine — I assume it's just that the translation was missing from the database.
Está bien — supongo que es solo que la base de datos faltaba la traducción.
I've reported it. "How long it that bridge" is the normal way a native English speaker would say this. The given answer (What is the length. . .) is possible, but very stilted (strange-sounding).