When computing the row size for a table row, what overhead should be accounted for?

When computing the row size for a table row, what overhead should be accounted for?
A . 48 bytes for ROWID, CREATEXID and DELETEXID only
B . 32 bytes for ROWI
C . CREATEXID, DELETEXID and the null vector
D . 32 bytes for ROWI
E . CREATEXID and DELETEXID and a variable number of bytes for the null vector if there are nullable columns
F . 24 bytes for ROWI
G . CREATEXID and DELETEXID plus null vector if there are nullable columns and record header depending on string columns

Answer: A