Which two statement is true concerning dropping a pluggable database (PDB)?

All the answers are incorrect.
A is incorrect: You can plug in the database again passing in the XML metadata file that you get when you unplugged the database, if “KEEP DATAFILES” (default) was specified when you dropped it.
B. is incorrect: you can keep the data file with the option “KEEP DATAFILES” when you drop a PDB

C, D and E are incorrect. The PDB could be in unplug (to keep datafiles) OR unplug/mounted to include data files:
To specify KEEP DATAFILES (the default), the PDB you want to drop must be unplugged.
To specify INCLUDING DATAFILES, the PDB you want to drop must be in mounted mode or it must be unplugged.

Here the Oracle documentation:

DROP PLUGGABLE DATABASE Prerequisites

You must be connected to a CDB.

The current container must be the root, you must be authenticated AS SYSDBA or AS SYSOPER, and the SYSDBA or SYSOPER privilege must be either granted to you commonly, or granted to you locally in the root and locally in PDB you want to drop.

To specify KEEP DATAFILES (the default), the PDB you want to drop must be unplugged.

To specify INCLUDING DATAFILES, the PDB you want to drop must be in mounted mode or it must be unplugged.

D(E)

D, E

alter pluggable database pd001 close ;

drop pluggable database pd001 ; ( note that default is keep datafiles )

drop pluggable database pd001 [ including datafiles ] ;