With this syntax, at first there doesn't seem to be an object though. But it could also be said, "it is difficult to answer the question." Then the question is clearly the object of "to answer." Anyway, I found this structure really difficult to understand; well, unusual at least.
It's been a long time since you wrote this, but if anyone else struggles with this, I just thought of a comparison: think of how the English verb look would work.
E.g. "These photos are hard to look at". This verb works the same way.
Here's add good a place as any, so:
I had to translate 'That is hard to believe' and it marked me wrong for answering with Det är svårt att tro på; the right answer omitted the på. So why aren't we omitting the på after the att here?
I think this works pretty much the same in Swedish and English: That is hard to believe = Det är svårt att tro but Det är svårt att tro på = That is hard to believe in.
The construction "is[/am/are] to be" is used not to describe but to stipulate something that has not yet come about, e.g. "The house is to be painted blue." It can also be used to give a suggestion, as a softer alternative to using the imperative mood, as in "This movie is not to be missed".
So, firstly this is not the meaning that we want for this translation, and furthermore, "The question is hard to be answered" is ungramatical. It is possible to say "The question is to be answered", and if we want to stipulate further details, we would need to use adverbs or adverbial phrases, such as "The question is to be answered truthfully". However, once you use an adjective in "The question is hard...", you are already in an entirely different construction that doesn't go along with "...to be answered".
difficult is the suggested translation, as you can see on top of this page, but hard works too. The machine tries to match your input to the closest accepted answer but it doesn't always work perfectly.
why not: "the question is hard to answer it"? ( I am not native English)
you don't need to say "it", because "the question" is the subject of that clause.
In English, "question" is used as the direction object of the verb "answer", without any preposition. "To answer to" has a different usage, for example: "You would have to answer to your big brother, if you don't do your chores" (because he told you to do it).
Shouldn't the Swedish course assess our understanding of Swedish, instead of our English grammar? This could be accepted with a reminder, similar to when typos happen.
That's actually quite a large problem, and one that is difficult to get right. Plus, a lot of our users take the course to improve their English as well, so it's already very difficult to draw the line in the case of e.g. idiomatics.