What should be done first in the decompression drill?

In a decompression drill, fitting the nearest oxygen mask is the first crucial step because it ensures that both cabin crew and passengers have immediate access to supplemental oxygen in the event of cabin depressurization. This priority is vital for maintaining consciousness and preventing hypoxia, which can occur rapidly after a decompression incident.

The need for quick access to oxygen masks is underscored by the fact that a rapid loss of cabin pressure can lead to dangerous conditions for everyone on board. Having oxygen available right away provides critical support to passengers and crew while further procedures are carried out, such as communicating necessary instructions or checking exits.

The other options focus on actions that may follow after ensuring that everyone has access to oxygen. For example, removing oxygen masks would only be relevant after the situation has stabilized, checking for open exits is a secondary safety measure, and commanding passengers to brace for impact applies to scenarios involving imminent crash landings rather than immediate decompression responses.