Your question is Assessing Overfitting vs Underfitting. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
You're comparing a few supervised learning models and need to decide whether poor performance is coming from a model that is too simple or one that is memorizing the training set.
How would you assess whether a model is overfitting or underfitting?