"I drink milk in the morning."
Translation:Eu bebo leite pela manhã.
First, it is not duo that has set it this way, it is the contributors, But, I agree with you completely. I would also wish that they not set the hover hints to represent the word itself, but rather, the word as it is understood in the sentence. Although, it could be argued that in the middle of the second set of lessons related to time, I should know the difference between "de, em, é and a" when talking about time. But, for the hints to recommend "de" and not actually have it as a possible answer is very frustrating. This is memorization, not utilization, and therefore, I would argue, as a standalone lesson, it would not be a teachable moment. But, amongst the other lessons, it is useful.