须：应当。指秘密的言谈也可能泄漏
Bushes have ears and eyes. <Fields have eyes,and woods have ears.>
隔(gé)
墙(qiáng)
须(xū)
有(yǒu yòu)
耳(ěr)
()
窗(chuāng)
外(wài)
岂(qǐ kǎi)
无(wú)
人(rén)
