Final answer:
The angle of repose for type C soil, which is likely to move easily, must be at most 30 degrees as it is the closest given option that represents a very low angle.
Step-by-step explanation:
The angle of repose is defined as the maximum angle at which a soil, sediment, or other loose material can accumulate on a slope without sliding. For type C soil, which is usually the weakest and most prone to movement, this angle is very low. The angle must be less than 34 degrees but since this exact value is not an option, the closest option given is 30 degrees (choice b). Therefore, in type C soil, the angle of repose must be at most 30 degrees.