The Harmony virus will destroy a computer system unless inoculated by an ... ...

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) a computer system unless inoculated
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Press: Set C - Misplaced and Redundant Modifiers