哪位知道FRM Handbook Chpt 7 里提到的straight bond 是什么含义？另外，156页“...a callable bond can be decomposed into a long position in a straight bond, minus a call option on the  bond price.”   Example 7.2 中也提到：“Issuance of a callable bond is equivalent to a short position in a straight bond plus a long call option on the bond price.” 是什么道理？Thanks.