"Where had you put it?"
Translation:Dove l'avevi messa?
Use lo,la,li,le and l' for direct objects. lo and la are singular, li and le are plural, and l' is used before vowels.
What is a direct object depends on the verb, some examples are what you give in dare, what you put in mettere and what you say in dire... that's the general idea, but you have to become familiar with each verb to know whether the 'it' is going to be a direct object or not.
Ci is a pronoun for when the thing is not a direct object. I find it more complicated and, rather than learning the rules, just remember individual verbs that it goes with. Such as ci penso, which means i think about it.
Check this out, it really helped me understand ci and ne.
I wrote Dove l'avevi messo because it can be masculin and femenin it, but I don't unterstand why it is wrong
"Dove l'avevi messo" isn't wrong. Like you said, lacrimae2, "it" can be masculine or feminine. They probably forgot to include it in their database of possible translations for this sentence. Just report it and after several reports they will add it.
The same thing happened to me. Does anyone know why this sentence doesn't allow 'messo' but requires 'messa'?
How do you know when to contract "lo" or "la" before a vowel? It seems like sometimes DL accepts it and sometimes it doesn't.