Which of the following sentence is 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