Which of These Was a Concern in the Conviction and Execution

Which of these was a concern in the conviction and execution of Cameron Todd Willingham?

A) The conviction was based on "junk science" in the area of arson detection.
B) The conviction relied on evidence supplied by a jail-house informant who was promised a reduced sentence.
C) The execution raised questions about whether an innocent man was put to death.
D) All of these were concerns.
E) None of these was a concern.