Which Is More Likely to Happen-Antigenic DRIFT, or Antigenic SHIFT-And

Which is more likely to happen-antigenic DRIFT, or antigenic SHIFT-and why?

A) Antigenic DRIFT-since infection with only a single virus is required, and the random mutations happen as the virus replicates in the infected person's cells.
B) Antigenic SHIFT-since infection with only a single virus is required, and the random mutations happen as the virus replicates in the infected person's cells.
C) Antigenic DRIFT-since random mutations occur more readily when only 1 virus is infecting a cell at a given time.
D) Antigenic SHIFT-since multiple viruses in a cell at once means more RNA polymerase to copy the RNA, and therefore more possibilities for much larger mistakes to be made in the copying (leading to mutations) .