Choice "C" is correct. A holder in due course (HDC) is a holder who takes an instrument for value, in good faith, and without notice of any claims or defenses. In addition, the instrument must be a negotiable instrument (commercial paper). While an exectory promise (i.e., one that has not yet been fulfilled) constitutes contract consideration, an executory promise does not constitute value for purposes of ascertaining if a holder is an HDC. Thus, Ralph cannot be an HDC until Ralph performs all that Ralph promised to perform.
Choice "d" is incorrect. One may be an HDC of any negotiable instrument. An instrument may be negotiable even if it is in bearer form.
Choice "a" is incorrect. One can become a holder in due course if he takes an instrument in good faith, and there is no indication that Ralph has not acted in good faith.
Choice "b" is incorrect. To become a holder in due course, a holder must take the instrument in good faith and give value.
