What Effect Can Indorsements Have on the Character of Negotiable

What effect can indorsements have on the character of negotiable instruments?

A) Indorsements can convert bearer paper to order paper,but not vice versa.
B) Indorsements can convert order paper to bearer paper,but not vice versa.
C) Indorsements can convert order paper to bearer paper,and can convert bearer paper to order paper.
D) Indorsements can convert order paper to bearer paper,and can convert bearer paper to order paper,so long as the instrument expressly allows such conversions.
E) Indorsement cannot change either bearer or order paper to the other classification.