I. Auxiliary Verb (have/ can/ was/ do) (= helping) used with a main verb. (e.g. Have you locked the door? Yes, I have. (= I have locked the door))
a. use do/ does/ did for the present and past simple. (e.g. Do you like opinions? Yes, I do. (= I like opinions))
b. can use auxiliary verbs to deny what somebody says (= say it is not true) (e.g. You're sitting in my place. No, I'm not. (= I'm not sitting in your place))
I1. use have you?/ isn't she?/ do they? etc. to show interest in what somebody has said or to show surprise. (e.g. I've just seen Simon. Oh, have you? How is he?)
Idiom 365
Let the Cat out of the Bag: to share a secret information that shouldn't be known by others
Example: It should be a serious confidential information until someone let the cat out of the bag.