"Yellow like a lemon."
Translation:Κίτρινο όπως ένα λεμόνι.
A slight one - some times they are interchangeable, other times only one or the other sounds natural because of how some expressions have become fixed in the language. For example, here both would make sense, but you would be much more likely to hear "σαν" with no article following it, when you're comparing the appearance of something with something else (e.g. κόκκινος σαν ντομάτα (red like a tomato), ελαφρύς σαν πούπουλο (light as a feather) etc).
You can also find a nice explanation of the syntactic difference of the two in teopap2's comment here: https://forum.duolingo.com/comment/17551907
I got this in a multiple choice question. WOuld it be possible for the question to be correct if I only pick ένα, but not both ένα and το λεμόνι? I feel like it is a little misleading if both ένα and το options are correct. Some multiple choice questions I have to stick to the word, some other ones like this question, I have to be a little more liberal and pick all that seem to be correct for me to pass the question.
The original sentence given is: : Κίτρινο όπως ένα λεμόνι. so "the" should not be a choice. If "the" was a choice it was a "wrong" answer in a multiple choice question. I agree giving both 'a" and "the" in this exercise was 'unfair'. The multiple choice questions are random and chosen by the bot which has not been receiving our edits. We have reported it.