Which of the following sentences are written correctly a. simmer the stew, it should be steaming, but not boiling, for about 20 minutes. b. simmer the stew ( it should be steaming, but not boiling) for about 20 minutes. c. simmer the stew {it should be steaming, but not boiling} for about 20 minutes. d. simmer the stew [it should be steaming, but not boiling] for about 20 minutes.