Why can't C1 drive C4?

[AnthonyLynn]

C1 can drive C4 models. According to regulations, a C1 driver's license allows driving all models of C2, C3, and C4. Driver's license classifications: A1: Large buses and A3, B1, B2, C1, C2, C3, C4, M A2: Tractor trucks and B1, B2, C1, C2, C3, C4, M A3: City buses and C1, C2, C3, C4 B1: Medium-sized buses and C1, C2, C3, C4, M (Medium-sized buses refer to buses with fewer than 19 seats, such as minibuses and vans) B2: Large trucks and C1, C2, C3, C4, M C1: Small cars and C2, C3 (Only passenger vehicles with fewer than 9 seats, such as sedans, are considered small cars) C2: Small automatic transmission cars C3: Low-speed trucks and C4 C4: Three-wheeled cars C5: Small automatic transmission passenger vehicles for the disabled (referring to five categories of people: those with right lower limb disabilities, lower limb disabilities, hearing impairments, right thumb missing, or finger end defects) D: Regular three-wheeled motorcycles and E E: Regular two-wheeled motorcycles and F F: Light motorcycles M: Wheeled self-propelled machinery N: Trolleybuses P: Trams Driver's license physical examination requirements are as follows: Motor vehicle drivers aged 70 and above (including 70) should undergo an annual physical examination, while those under 70 do not need to.