In this exercise I got this tense wrong (as I usually do for the verb devoir). The linked lesson on this topic is misleading. It says that when devoir is used in the imparfait e.g je devais, it means I was supposed to do (an obligation, in most cases not met) whereas it has a different meaning in the passé composé where j’ai dû = I had to do, or I must have done (an obligation that was met, or a hypothesis on a past situation). This doesn’t seem to be correct in practice, where if it is a repeated action we would still use the imparfait.
For example, this week’s exercise asked us to translate “... that we had to develop (use nous)”. I put: “que nous avons dû développer” which is in accord with the lesson but was marked as incorrect, with one of the given options being “que nous devions développer”. Although I can see the logic in that, it appears on the surface to directly contradict what the linked lesson tells us.
(Interestingly, in the full text of the passage after the exercise, they used “qu’il fallait développer” which does get around this problem, but it is sort of cheating, as we were told to use “nous” when translating this particular phrase, haha)
