Final answer:
The correct answer is b) Importin. Importin is a protein that plays a role in the transport of molecules into the nucleus of a cell.
Step-by-step explanation:
The correct answer is b) Importin.
Importin is a protein that plays a role in the transport of molecules into the nucleus of a cell. It recognizes a specific sequence called the nuclear localization signal (NLS) on the molecules that need to be imported and helps facilitate their transport.
In this question, the student is asking which factor blocks the regulation of import by Pho4. Since importin is responsible for the import of molecules into the nucleus, blocking its function would disrupt the regulation of import by Pho4.