简述《灵枢•营卫生会》篇中的“上焦如雾，中焦如沤，下焦如渎”的含义。

An unconscious client has been admitted with a head injury. Which of the following nursing diagnoses would receive the greatest priority in the plan of care

A．Disturbed sensory perception related to decreased level of consciousness.

B．Ineffective airway clearance related to inability to remove respiratory secretions.

C．Impaired gas exchange related to shallow irregular breathing.

D．Risk for injury related to disorientation and decreased level of consciousness.