The following information is available for two bonds: Bond X is callable and has an option-adjusted spread (OAS) of 55bp. Similar bonds have a Z-spread of 68bp and a nominal spread of 60bp. Bond Y is putable and has an OAS of 100bp. Similar bonds have a Z-spread of 78bp and a nominal spread of 66bp. The embedded option cost for Bond:（）
A. X is 5bp.
B. X is 8bp.
C. X is 13bp.
