1 sentence

1. 他们约定好以窗台上的花盆作为暗号。

   tā​men yuē​dìng​hǎo yǐ chuāng​tái shàng de huā​pén zuò​wéi àn​hào.

   They agreed to use the flowerpot on the windowsill as a signal.

   Source: Dong Chinese Dictionary