There is a distinction between the soft d and hard t sounds in French as well; just listen very closely for it (repeat the sound several times if necessary). If you still can't hear the distinction after seeing the answer or if it's clearly wrong, I'd suggest reporting an error. Sometimes you may just have to deal with the lost heart :(
If you are unsure about the pronounciation difference I suggest using Google Translate to speak the phrases. It has been helpful to me to sort out this sort of thing.
Anyways, "livre" is masculine so it would be "ton livre" (as singular) and "tes livres" (as plural). "Te" is a reflexive pronoun that can be used with pronomial verbs only such as these: http://french.about.com/od/grammar/a/pronominalverbs.htm
As TopTenTiger said, you will never encounter the phrase "te livre". But for cases like "le livre" and "les livres", you can distinguish the pronunciation by listening for the vowel sound. "Le" has that "ooh" sound like in "book", whereas "les" is nearly identical to the english word "lay" (minus the horrific accent). To distinguish between te, tes, me, mes, se, ses, etc, it's the same rule each time.