not to say还是not to mention

请看下面一道题：

They own two cars, not to _________ a motorbike.

A. speak                        B. say                        C. talk                        D. mention

【分析】此题很容易根据“我们拥有两辆小汽车，更不用说一辆摩托车了”这一中文语境而选择B，其实最佳答案为D。因为not to say 和 not to mention 均为习语，其含义区别甚大：not to mention＝更不用说，此外还有；not to say＝虽不能说，即使不能说。如：

He can speak French and Japanese, not to mention English. 他会法语和日语，更不用说英语了。

David is handsome and smart, not to mention being a good athlete. 戴维漂亮精明，而且还是个优秀的运动员。

It is warm, not to say hot. 天气虽说不上热，但也够暖了。(from www.nmet168.com)

He was impolite, not to say rude. 他即使不是粗鲁，至少也是没有礼貌。