Tsume 1 (problem) - Level beginner

This is the first problem in a small book I have, check-mate in 1 move.

The opponent's King is in the back right corner of the board. You have a Pawn on the third row in front of it.

In your drop zone, you have a Rook, a Gold General and a Silver General available.

Please use the spoiler tag to post your answer :)

::: spoiler Solution Drop Gold General in front of the King at 1二, protected by the Pawn at 1三.

Wrong moves:

• dropping the Rook at 1二, at 3一 or at 4一 lets the King escape to 2一,
• dropping the Silver General at 1二 lets the King escape to 2二
• dropping a Gold or Silver General at 2二 lets the King take General back at 2二, since it isn't protected by the Pawn. :::

Reminder of the movements of the pieces: