The Following Argument Is Valid or Forceful

Multiple Choice

The following argument is valid or forceful. Identify the irrelevant premise: There

A) Lee Harvey Oswald could not have assassinated President Kennedy on his own.
B) Suspicious figures were seen on the grassy knoll just before the assassination.
C) Oswald must have had help from co-conspirators.
D) If Oswald could not have assassinated Kennedy on his own, he must have had help from co-conspirators.