It must always use the relative pronoun. Use the case system of the relative pronoun, and indicate which number and case the Latin equivalent would be in. The students don't like Latin. They see the cars. George likes hard boiled eggs.
Many students are never prepared for class.
The rocks fell off the cliff. Betty avoids my brother. We've done all the difficult work. Now you have only to learn the declensional system of the Latin relative pronoun and practice with it. The Latin relative pronoun has a full declensional system.