Let $\mathrm{S}$ be the specification: "Instructors teach courses. Students register for courses. Courses are allocated classrooms. Instructors guide students." Which one of the following $\mathrm{ER}$ diagrams CORRECTLY represents $\mathrm{S}$?
- $\text{(i)}$
- $\text{(ii)}$
- $\text{(iii)}$
- $\text{(iv)}$