What is skipped in front of second sentence?
"That's" are left out at the beginning of the sentence. The sentence should be "That's inadvisable" During informal conversations, you may notice that words are left out of sentences. This is because the remainder of the sentence can stand alone and is perfectly clear without the help of other words. Words that are commonly left out are helping verbs, articles, possessives, and personal pronouns. Ex: (Do you) Know where it is? A: How's Annie? B:(She is) Not feeling well. A: How are you? B: (I am) Doing well. Ex: (Are) You ready?