Translation:The boy eats a mandarin with bread.
I think the confusion comes from a lot of mandarins being marketed as tangerines in the USA for some reason, but even so they're still different fruits there and both should be acceptable translations, in addition to the alternative spelling "mandarine". I included this information when I reported it so hopefully "tangerine", "mandarin" and "mandarine" will all be acceptable. I confirmed with some Romanian friends that they don't have a separate word for tangerine so I'd like to think this will be fine. For what it's worth I'm British and in the UK a mandarin is just a mandarin, each different type of orange has its own name and that's that. Also I wouldn't have thought mandarins are even popular enough to be used as a catch-all term over simply "orange". I feel a little pedantic discussing this I'm just slightly annoyed such a seemingly obvious answer is marked wrong.
I have just completed eight out of the first eleven lessons and find that the program still needs a fair bit of polishing. There were quite a number of cases where only one word was accepted in translation whereas there should be other choices accepted e.g the translation of "scump" is only accepted as "expensive" but "dear" should also be accepted. I tried "chook" as a translation for "gaina" since the picture showed a rather mature hen, but I guess that is Australian idiom. Also a list of modified letters is required just as there are in the French and German lessons since there is no way I know of inserting symbols as in Word. The program has only just been launched and I am sure it will improve in time.
In UK English there are mandarins, tangerines, clementines and satsumas and they are all different but they all belong to the orange family. I always think to translate mandarină as mandarin but this course suggests tangerine. I believe mandarine is maybe the correct US English form. Do any of these other words resonate in other languages? (I believe the French have mandarine and clementine.)
Mandarin should be the correct translation regardless of where you are in the world, even if you're in the US where mandarins are sometimes marketed as tangerines. Also, I think you're getting your fruits mixed up a bit - a nectarine is a type of peach (with smooth instead of fuzzy skin), not an orange, the other four you listed are indeed types of oranges though. Satsuma is simply a seedless mandarin. Clementine is a hybrid of mandarin and orange. Tangerines are thought to be closely related to or are a variety of mandarin. Seems to me that mandarin or some variation thereof is common to many languages, whilst for the other three either the English terms are borrowed or they simply don't exist and just say mandarin instead.