The verbal instructions involve oral communications from instructors with spectators or students to generate a good project for their studies.
The other words such as “written or detailed” are not going to fit grammatically in the above case as they do not represent verbal communication with students.
Thus, the options (a), (d) and (b) are incorrect.
The verbal instructions involve oral communications from instructors with spectators or students to generate a good project for their studies.
Therefore, the correct option is – C. oral