What are the factors that may affect the calculation of OBQ value?

A. Residues on tank floors, the age of the vessel and previous cargoes carried.
B. Residues on tank floors and previous cargoes carried.
C. Residues on tank floors and structures, and previous cargoes carried.
D. Residues on tank floors and structures, and these will vary with the age of the vessel and previous cargoes carried.