大多数交易都是私下进行的。

Most of the deals were done ___behind ___closed ___doors.

影响整个世界的决定都是在私下做出的，并且是绝密的。

Decisions which affect the whole world are made ___behind ___closed ___doors and are top secret.

谈判在私下进行，以避免媒体审查。

The negotiations took place ___behind ___closed ___doors to avoid media scrutiny.