Which USP $797(2022)$ requirement must be met in order to use a single$-$dose vial for up to $12$ hours?

Select one:

a$.$ It must be stored in the refrigerator.

b$.$ It must be covered with a vial seal after puncture or entry.

c$.$ It must be stored in the PEC after puncture or entry.

d$.$ It must be punctured or entered in the PEC.