What feature is mandatory for taxicabs regarding their meters?

The requirement that a taxicab's meter must be accurately non-removable and permanently sealed is critical in ensuring the integrity and reliability of fare calculations. This feature prevents tampering, ensuring that the meter consistently provides accurate readings based on distance traveled and time taken.

By being permanently sealed, the meter protects against unauthorized adjustments that could result in fare manipulation, which helps build trust in the service from customers. This is important for regulatory compliance, as many jurisdictions have strict requirements related to fare devices to prevent fraud and protect public interests.

The other features mentioned are not universally mandated; for instance, removable meters or frequent recalibrations may be permissible in some areas, but they are not considered essential for accuracy or security in the same way that a sealed meter is. Displaying multiple fares could enhance service but is not a universal requirement that addresses the fundamental need for accurate and tamper-proof pricing. Thus, the correct option emphasizes the critical necessity of security and precision in taxicab fare meters.