Multiple choice being too easy.
Wouldn't it be better to make the incorrect answers that are in English to make sense? A lot of the time the question could be in any language and I would still get it right as 2 of options are just nonsense.
I agree. I found it useful (in french) when the multiple choice questions showed that 'tu' and 'vous' can be translated to 'you'. In later questions it just got silly and in a glance you could identify which sentences were wrong.
Multiple choice should still come if multiple translations are possible. Wrong answers should not not be compete nonsense though (changing the time from present to past, changing the number of objects, using the feminine form instead of the masculine... might be better).
Often you can pick it simply by looking at one word in the English and finding the word for it in the other language without even considering the rest of the sentence. Also, these words are often extremely similar so it is simply looking for 'the word that looks the same' instead of actually testing language skills.
I've posted some of these multiple choice screenshots on Face because they are so absurd. The questions need to be formed more intelligently, with specific words manipulated or as suggested already, changes of tense or gender. All options should sound possible. "I am an American sandwich" is not a reasonable option. Also, an eye should be out there for cognates, as mentioned. "Il a un canard" and "Il a un chien" aren't bad choices, when you add "Il a un éléphant", it is ruined since that last option is transparent.
In setting multiple choices, remember that the differences between the options should relate to the grammatical point that is being tested.
For example, if the unit is about subjunctive verbs, a question with answers that differ only in one of the nouns used in otherwise similar sentences misdirects the students to something other than the point being studied, so add nothing to the student's understanding of the topic.
Because of this defect in many of your questions, too many can also be solved with zero knowledge of the relevant topic.
I disapprove of multiple tests on the whole. In Maths, you are told that one answer is the correct one. So if you have done the calculations and your answer is not one of the opinions, you know it is wrong. However, Duolingo has a twist, more than one answer could be correct. It might be that two or sometimes all three answers are correct. This, of course, can't happen in Maths, but with translating sentences it makes the test more demanding.