A contains an error: "and then she publishes them under a false name" is an independent clause and should have a comma before it.
B contains an error, as the comma should be before "but", not after it, for the same reason as A.
C correctly shows what should have been done in A and B.
D should not have a comma after "but".
C is the correct answer.
Answer:
By my opinion the answer is "secure"
