This exercise requires you to put on your extra powerful thinking caps. Using concepts we have discussed in class, discuss why the imperative sentences in the second column of (a) and (b) below are grammatical, but the imperative clauses in (c) are not grammatical. (For this exercise, you will have to put on your thinking cap and go beyond what we have explicitly discussed in class, but the concepts taught are relevant.) a. John is running. Run! John is eating. Eat! b. John is friendly. Be friendly! John is good. Be good! C. John is sleepy. *Be sleepy! John is hungry. *Be hungry!