Although World War II ended nearly a half century ago, Russia and Japan ... ...

Determine whether or not there is an error in the underlined portion of the sentence above. If there is no error, select answer choice "A".
(A) have not signed a formal peace treaty; and both countries have been
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Press: Set E - Faulty Verb Tense