Which of the following scenarios does NOT normally occur on a nuclear pore complex?

A) A protein complex is imported into the nucleus, with ONLY one of its subunits containing a nuclear localization signal (NLS).
B) In a single pore, an NLS-containing protein is imported, while at the same time a nuclear export signal (NES)-containing protein is exported.
C) A nuclear import receptor is exported from the nucleus through the pore.
D) A protein is imported on its own through the pore, without the need for a separate import receptor.
E) All of the above are possible scenarios and occur naturally.