他微笑着点头表示收到了礼物。

He smiled and nodded in ___acknowledgement of receiving the gift.

他在演讲开始时表达了对赞助商的感谢。

He started his speech with an ___acknowledgement to the sponsors.

请在收到包裹后发送一封确认邮件。

Please send an ___acknowledgement email after receiving the package.