I think the answer "She doesn't tell him this" is correct. This is the exact trandlation of "Sie sagt ES ihm nicht". The correct translation provided by the app is imprecise. The app suggests the correct answer is "She does not tell him". Now, the German for this would be "Sie sagt ihm nicht". The "es" in the task sentence is clearly a direct object and refers to what the subject tells the indirect object. Therefore, a translation to English with two objects shouldn't be deemed wrong.
These pronouns in their case variants are killing me! Is there a simple table or some kind of easy to remember rule about when to use each one? I've been trying to learn the basics of German conversation using a more natural approach, that is to say without diving too much into grammar details, and Duo is perfect for this. But I seem to have hit a wall here.
direct object (DO) is in accusative case
indirect object (IO) is in dative case
There are a few exceptions with dative verbs such as helfen (DO in dative) and kosten (all objects in accusative), but the general rule is above.
What might be a challenge, is the fact that prepositions often ask for a specific case hence you will need to use the correct form of a pronoun with a specific preposition. Examples are mit or bei which both demand dative (hence: mit ihm, bei ihr) or um which usually demands accusative with personal pronouns (hence um ihn; don't confuse the preposition um, though, with the conjunction um which may be followed by a pronoun in dative: um ihn zu sehen [Fn]).
Here is a chart:
Fn: Accusative as ihn is the DO of sehen.
"sagt ihm" means "am saying to him", and "nicht" means "not". When you combine "am" and "not" you get, "don't" (do not).
You used the word, "won't" (will not). And, although the end result is the same to 'him' (he doesn't get told), the intent of the subject is quite different. Like Donald Trump withholding his tax returns; He could and should release his taxes, but he WON'T (will not). Maybe that's why he DIDN'T (did not) win the popular vote.
I see a lot of people trying a lot of things that are being kicked back as wrong, although, some answers do seem almost correct. I think I understand this now. I just remember that 'ihm' means "to...him", then I try to make the sentence work with that.
"She doesn't tell him" - Duo's Primary Correct Answer
"She doesn't say it to him." - Correct (my answer)
"She doesn't say/tell it to him." - ? (Haven't tried this yet.)
"She doesn't say/tell that to him." - ? (Haven't tried this yet.)
"She doesn't say/tell this to him." - ? (Haven't tried this yet.)
"She doesn't tell him it." - Wrong. (although, "it" doesn't sound correct at the end...maybe 'that' or 'this' would fit better.)
"She doesn't say/tell him this." - ? (Haven't tried this yet.)
"She doesn't say/tell him that." - ? (Haven't tried this yet.)
I'm not certain, but using a translation app and my Duo lesson knowledge thus far, I believe the follow to be mostly correct:
"Sie sagt, es ist nicht ihm." <=> "She is saying it is (it's) not him".
"Sie sagt es ihm nicht." <=> "She does not tell him." or "She does not say IT TO him."