单选题 The shop assistants said that they could never be ______ polite to their customers.
A. so B. enough C. very D. too

【正确答案】 D
【答案解析】[解析] 该题考查副词too的用法。含有too的句子中，如果出现否定词“never...too...”，则解释为“太……也不为过”。