Also, to ALL MX2 students I suggest purchasing the calculator CASIO fx-100 AU PLUS for it's ability to do COMPLEX NUMBER OPERATIONS in the exam! This calculator is indeed, board approved!
For the multiple choice question, whilst the method provided by Jake is essentially what a short response requires, multiple choice can be hastened by simply SUBSTITUTING x=1-2i directly in! If what I typed into the calculator is right, A, B and C ALL don't equate to 0.
Multiple choice tricks.
FURTHER EDITING: In fact, there is one last trick. A and B are automatically wrong because the last root has to be a fraction! Not an integer! Non integral (adjective for integer in this case) roots are the only cause the leading to coefficient to deviate from 1.
In the long method, this means that the (ax+b) could be SAFELY written as (x+b)! Then, only constants have to be equated.