What does the author imply by "Until now such bonds have largely been the preserv

Whatd oestheauthorimplyby"Untilnowsuchbondshavelargelybeenthepreserveofrich-countr yis-suers"(Line3-4,Para.2)?（）

[A]Thecatastr ophebondsaremainlyreservedbyrichcountr ies.

[B]onlyrichcountr ieshavetheabilitytoissuethecatastr ophebonds.

[C]Richcountr iesseldomissuethecatastr ophebonds.

[D]Mostofthecatastr ophebondsareraisedinrichcountr ies.