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.