Learn Italian: Il proprietario deve identificare la custodia nella foto. - The owner must identify the case in the photo.

You would ask, Di chi è la custodia? The structure is always di chi + the verb essere (to be) + the object. The proprietario (owner) in our sentence is the one who would step forward to answer that question!

The word foto ends in "-o", so why does it use the feminine nella (in the) instead of the masculine nel?

Foto is short for fotografia, which is a feminine noun. When Italian words are shortened, they keep their original gender. That is why it takes the feminine article la, and when combined with the preposition in (in), it becomes nella foto.

Does custodia mean "custody" here, like in a legal sense?

It can in other contexts, but in everyday Italian, una custodia is usually a physical case, cover, or sleeve used to protect an object. For example, a phone case is a custodia per il telefono. In this sentence, the owner is likely looking at a photo of a lost or stolen case to identify it.

Why is identificare left in its infinitive (dictionary) form rather than being conjugated?