单选题 I ______ tell her the truth.

【正确答案】 B
【答案解析】此题涉及“can not but+原形动词”的习惯用法。
可能错选A。注意,cannot help的正确使用方法是“cannot help+动词现在分词”,如:
The small business men could not help increasing the prices of their goods.