Alba: I don’t intend to vote for Senator Frank in the next election. She is not a strong supporter of the war against crime.

Tam: But Senator Frank sponsored the latest anticrime law passed by the Senate.

Alba: If Senator Frank sponsored it, it can’t be a very strong anticrime law.

Which of the following identifies the most serious logical flaw in Alba’s reasoning?

(A) The facts she presents do not support her conclusion that Senator Frank is soft on crime.

(B) She assumes without proof that crime is the most important issue in the upcoming election.

(C) She argues in a circle, using an unsupported assertion to dismiss conflicting evidence.

(D) She attacks Senator Frank on personal grounds rather than on he merit as a political leader.

(E) In deciding not to vote for Senator Frank, she fails to consider issues other than crime.

C中的argue in a circle应该怎样理解？