The lesson states that using the pronoun "on" is equivalent to using the pronoun "nous" to indicate "we", but when appearing in a quiz it says that using "nous" is incorrect and "on" is correct. If there is a significant difference in usage, then it should be explained in the lesson, as it fails to do so. If it states that they are synonymous and exchangeable in use, then correction needs to be to that effect. I can't learn how to use them for what they mean when in dictation they are one thing but are another thing entirely when put into practice.