In Which of the Following Situations Has Conversion NOT Occurred

In which of the following situations has conversion NOT occurred?

A) When an instrument is paid on a forged indorsement.
B) When a drawee to whom a draft is delivered for acceptance properly returns it upon request.
C) When any person to whom an instrument is delivered for payment refuses on demand to pay or to return it.
D) When a bank pays an instrument containing only one of two required indorsements.