Translation:The Klingon glottal stop
Yes. The first comment is pointing out what to type if you are using the keyboard. My point was that the word tiles don't have ' as one of the choices. But it was marked correct when I selected only "the" and "letter". There was no apostrophe to choose. So the correct answer missed the point entirely.
In my case, however, having first read the Tips/Notes, and knowing the limitations of the DL course (in this case, not recognizing ' as a letter), after seeing that there was no tile for " ' " among the word tiles, I both (1) got the answer correct (by choosing "the letter" [blank]), and (2) fully understood the meaning of the exercise - on the first attempt. So, it is possible for that convergence of events to happen. :-) It's not missing the point if you understand all of these factors.
This is the only letter in the alphabet that will have this issue, so I'm not sure it's worth making a big deal out of fixing the bug if it's not fixable. It's annoying, yes, but it's just one letter out of the alphabet. We have so many more important things yet to learn!
I'm not sure whether Duolingo is sometimes dropping the apostrophe or if it's just easy to miss because it's such a small mark, but you're not the first person to have this confusion.
What appears to be an apostrophe in Klingon is actually a full alphabetic letter. The name of this letter does not follow the normal pattern for naming letters. Instead this letter is called the qaghwI'. The word qaghwI' is not a translation for the word "letter", but is the name of a particular letter of the alphabet.
I hope that helps. But please ask more questions if there is still any confusion.
If what you are saying is true, then it seems to me that the English translation of qaghwI' should be "a/the qaghwI' " rather than "a/the letter ' ' ' ". Or perhaps change the spelling to something more understandable in English (e.g. kagwi) like you do for martaq (Martok), torgh (Torg), wo'rIv (Worf).
Please notice that the last letter of qaghwI' before the qaghwI' is a capital i, not a lower case L. The font Duolingo uses does not make the distinction very clear, but if you look carefully at the bottom of the letters, you can see a little curl on the bottom of the lower case L. Compare I and l and see if you can see the difference.
Learner feedback: it should say the letter, but requires you to te ype the letter ' (if the ' is not typed, it is marked wrong)
If I'm reading this correctly, (a) Duo is now requiring you to actually type a qaghwI' (') in order to get this marked right; and (b) this learner is complaining that ghaH has to actually type a qaghwI' in order to get the mark.
I went through the lesson a whole bunch of times trying to get this exercise so I could test it, but never did. Rest assured that just as if an exercise asks you to translate ghay your answer should be either gh or the letter gh, when it asks you to translate qaghwI' you should be able to respond with ' or the letter '. An answer of simply the letter should be marked wrong for any exercise here.
When on the Duolingo webpages or apps, in lessons or in the forums, the font is not great for Klingon, but if you look really carefully, you will see a small curl at the bottom of the lowercase L and no curl at the bottom of the uppercase i.
More importantly, Klingon syllable structure is very simple and fairly strict, so it's often quite easy to tell by the position of the letter which it is. There are NEVER two adjacent vowels, so if the l/I is next to a vowel, it must be a lowercase L. And every consonant must have at least one vowel adjacent to it (with some rare exceptions for gh and ' and noting that tlh, ch, gh, and ng each count as single consonants).
So looking at the word qaghwI', you might be able to tell that there is no curl at the bottom, but you can easily see that it has the consonant w on one side and the consonant ' on the other side and so definitely must be the vowel written with uppercase i.