电话那头，我轻声回应着‘嗯嗯’，表示我在认真听她说话。

On the phone, I softly responded with "___um-hum" to show I was listening carefully.

嗯哼...我得先查一下日程表才能给你答复。

___Um-hum... I need to check my schedule before I can give you an answer.