问题：

[单选] With reference to rules governing steering gear, which one of the following rules is incorrect? （）

A . It is required that all ships are provided with two independent steering gear systems that is one main and one auxiliary
B . The auxiliary gear could be power operated in passenger ships
C . The auxiliary gear must be of adequate strength and sufficient to steer a ship at navigable speed
D . All moving parts of the steering gear must be guarded against any possible damage