Translation:My father is an architect, not an engineer.
Agreed; contractions should be avoided in formal writing, or at least that's what they always told us in school! ;) That said, i absolutely think that father's or dad's should be accepted-that's what i put and got marked wrong! I don't see anyone thinking, "your father's what..?" in confusion of the possessive except for maybe a millisecond.
Oh, right, well you've caught me in a chatty mood today (sorry!). :-)
What is right and what is wrong in writing? It seems no two people have the same point of view. Some eschew the advice of grammarians, some adhere slavishly to it, but in the end everyone judges the quality of your writing based on their own prejudices and beliefs. We've both said what we think, but Duolingo has to make a hard decision - accept "father's" or reject it.
Obviously in speech you'll usually hear "fathers"/"father's" and not "father is" - there is no question about that! In writing, accepting "father's" both as "father is" and the possessive case takes us into "it's" territory in reverse. How many times have you seen people use "it's" as a possessive and you've wanted to tell the writer, in no uncertain terms, that "it's" means "it is". I would expect to be criticised for using "father's" for anything other than possessive "father's".
The contraction is perfectly correct. Far more so than many of the words duolingo accepts.
The only reason to avoid it while learning is because the same contraction can be used for several words.
It's my father's job (apostrophe s = possessive) My father's an engineer (apostrophe s = is) My father's got many tools (apostrophe s = has)
and frankly, that's a silly reason. We're not learning to write legal briefs. Some contractions are slang (gonna go, wanna go, shoulda gone) but most are perfectly normal. If you allow "won't" and "can't" then you should allow "father's."