参考答案

正确答案：D
解析：Sarah Pittman询问了Sam Timmons是否对工作感兴趣(if you are interested in doing the work)，工作所需时间(how long you think it will take)和费用(how much you would charge to do it)的相关问题。因此将表达方式改换为An estimate of charges的选项(D)是正确答案。