The English version of this sentence is terrible - ambiguous and virtually meaningless. You would always say a child loves "its/his/her" mother, never "the" mother, unless (conceivably) the child loves somebody else's mother, in which case whose?
And the child "has loved" the mother - this means the child has loved the mother for a period of time and then stopped loving her for some reason - somewhat absurd. If the mother is dead, you would say "the child loved its mother", not "has loved".
Does this sentence actually mean "the child loved its mother" in Greek? If so then that should be the required translation - but it is marked wrong. Or is this also a meaningless sentence in Greek?
First of all, let me say that I do agree with you. This isn't quite the daily used sentence, you probably wouldn't say something like that, let alone hear someone else say it. "The child loved its mother" would probably make a bit more sense.
However, this is Duolingo, and it's pretty famous for that exact kind of sentences. As far as I know, almost every language course has some sentences that seemingly make no sense or sound absolutely absurd, yet it's not that big of a deal. Some of them sound unintentionally funny, wrong even, because there is literally no context. And that's because sometimes there is only a sentence structure to be shown. At least that's what I think. That in some cases, with a random sentence example, you kind of get an idea how the structure works, how words come to place, and later you can tell how it could be modified and actually be used.
So please, it would be better to not try to make sense out of sentences like this one, because... there isn't any. Thank you for your comment though ^.^
If you wanted to be absolutely literal it doesn't make sense but these sentences are created out of the necessity to use certain words and syntax. Let's look at a broader picture. The present perfect is used for an action that started in the past and has some definite effect in the present not that has stopped. So, if they are in the habit of watching a certain TV serial in which there is a mother figure it is possible to say that "he has loved the character of the mother since the show began".
It's still not brilliant but both grammatically and logically plausible.
Well done - you have indeed found a context in which the sentence makes perfect sense. Apologies for the complaint - this is clearly not a great sentence, but as you both say, these things come up in language courses. It just confused me because I wasn't quite sure whether the Greek version had a wider meaning, and the ambiguity of the English didn't make that quite clear. But it's a great course overall!
Oh, no need to apologise. After reviewing these thousands of sentences we've become trained in figuring out (or pretending to figure) out what in the world some of them mean. It's a new kind of quiz. :-) There is even a site on the net (don't recall the name) with strange sentences that have appeared on Duo. My all time favorite was in German see it here
Best wishes on all your endeavors