核心句型：
I'm so sorry to keep you cooling your heels.
非常抱歉让您久等了。
cool one's heels字面理解意思是：“冷却某人的脚后跟”。这里的heel一开始不是指人的脚后跟，而是指马蹄。在火车、汽车发明之前，马匹是人类最主要的交通工具，在长途旅行中，经过长时间跋涉，马蹄就会过度发热，骑马的人不得不中断旅行让马休息一下。现在，这个词已经转义为：“苦苦等候，坐冷板凳”了。因此，当美国人说"I'm so sorry to keep you cooling your heels."时，他/她要表达的意思就是:"I'm so sorry to keep you waiting for so long."、"I'm sorry to have you kicking your heels for so long."。
情景对白：
Benjamin: I'm so sorry to keep you cooling your heels. Have a seat.
本杰明：很抱歉让你久等了，请坐。
Client: I hope you were expecting me. Here are the details about our cooperation. Please have a look at it.
客户：我想你之前也等着我来吧。这是我们合作的详细资料，请看一下。
搭配句积累：
①I was on emergency temporarily and couldn't get away immediately.
我临时有事，一下子走不开。
②Let's begin right now.
我们马上开始吧。
③We were caught in traffic jam.
我们堵车了。
④We will serve you as quickly as possible.
我们会尽快为您服务。
单词：
1. temporarily adv. 临时地
His job here is only temporary...
他在这儿的工作只是临时的。
Most adolescent problems are temporary.
多数青少年问题是暂时性的。
The peace agreement has at least temporarily halted the civil war...
该和平协定至少暂时停止了内战。
2. traffic jam 交通堵塞
The concurrent political rallies caused a traffic jam.
同时举行的政治集会引起了交通堵塞。
His car was stalled in a traffic jam.
他的车子在交通阻塞中动弹不得。
He was late because he was caught in the traffic jam.
他迟到了，因为遇上了交通阻塞。