Where? "The korean strawberry is very delicious" ?
In the sentence: "Apple is the best fruit in the world" article is not necessary. Using the word apple in the general sense.
I fail to see the necessity of an article in that sentence.
I would appreciate if you could elaborate. I might be wrong...
But if it were saying "Korean strawberries are very good," wouldn't it have been "한국 딸기는 아주 좋았습니다?" Even if the same basic meaning is coming across, it's technically not what the sentence is saying, so perhaps it shouldn't be translated that way. I don't know, you could be right. I don't think it was too unreasonable for "good" to be marked as incorrect, though.