Select the most appropriate meaning of the underlined idiom in the given sentence.

She may be the Principal but it is the school administrator who rules the roost.

is in complete control

The most appropriate meaning of the underlined idiom "rules the roost" in the given sentence is is in complete control.

The idiom "rules the roost" is used to describe someone who has the most power and authority in a group or situation. In the given sentence, the school administrator is in complete control of the school, even though the principal is the highest-ranking official.

The other options are not as accurate descriptions of the idiom.

• Is proved right does not accurately describe the meaning of the idiom, as it is not about being correct or incorrect.
• Is totally submissive suggests that the school administrator is subservient to the principal, which is not the case.
• Is dependent upon her suggests that the school administrator needs the principal's permission to do anything, which is also not the case.