Concept:The phrase "cut the ground from under my feet" is an idiom that means weakening or destroying someone's position or advantage.Explanation:The idiom suggests removing the support a person stands on.When the ground is cut away, the person loses stability and cannot continue smoothly.In this sentence, revealing the information will take away the speaker's advantage.As a result, the speaker's plans will be destroyed or made ineffective.So "ruin my plans" gives the correct meaning.Answer:A. ruin my plans