Under GB/T 22485-2021 (Taxi Passenger Transport Service Specifications), what is the mandatory personal grooming and dress code standard for a taxi driver on duty?

1. Wear neat, clean attire or standardized corporate uniform, maintain clean personal grooming, and never wear slippers, flip-flops, or bare chests
2. Drivers may wear casual home slippers in summer to stay cool during long shifts
3. Drivers are required to wear formal business three-piece suits and bowties at all times
4. Any clothing is acceptable as long as sunglasses are worn during daytime