Carl writes a check for $500, payable to the order of Fred. Fred owes Greta $600, so Fred changes the 5 to a 6 and endorses it over it to Greta to...

Carl writes a check for $500, payable to the order of Fred. Fred owes Greta $600, so Fred changes the 5 to a 6 and endorses it over it to Greta to pay the debt. Which of the following statements is true? 

A. Greta isn't a holder in due course because she didn't take for value.  

B. Greta is a holder in due course because she isn't the one who altered the instrument.   

C. Greta is a holder in due course unless she knew Fred altered the instrument.   

D. Greta isn't a holder in due course because the instrument has been altered.