I would appreciate ------back this afternoon .

1. 答案：C.
2. 翻译：今天下午你回电的话,我会很感激的.
3. 解释：
1）此题考查appreciate意为“感激/感谢”的搭配.
2）固定搭配：appreciate sb doing sth = appreciate one's doing sth,意思是“感激/感谢某人做某事”.
所以该题答案为your calling...或you calling...
3）其中的sb/one's doing sth在语法上被称为动名词的复合结构.
再如：mind sb/one's doing sth “介意某人做某事”
例：Do you mind my/me smoking? 你介意我抽烟吗?