Which of These Statements Concerning American Political Parties Is NOT

Which of these statements concerning American political parties is NOT correct?

A) The vagueness of party membership is a good indicator of the insubstantial nature of American parties.
B) Parties are fairly well-constructed organizations, led by party professionals and committed to a set of policies and positions.
C) Independent candidates can sometimes force themselves on the party through primaries or caucuses open to the public.
D) American parties are more candidate-centered than parties in most other countries.
E) all of the above