This is the second part of a study published in a previous issue of this Journal whose main goal was to analyze and document the types of knowledge that university students exhibit to deal with fundamental issues that they had studied in a first ordinary differential equation course. Here, we focus on analyzing and discussing the following research questions: (ii)~How do students make sense of, interpret and deal with the concept of solution to an ODE? (iii)~What systems of representation do they use to represent and explore the information embedded in those questions in order to answer them? And, to what extent do the students privilege the use of certain type of representation?