Why Are Eurobonds Rarely Rated by Well-Known Security Rating Firms

Why are Eurobonds rarely rated by well-known security rating firms?

A) Firms issuing Eurobonds typically have very high credit ratings which suggest that their bonds carry very low credit risks.
B) Eurobonds can be issued by any entity anywhere,so rating the credit risk of Eurobonds cannot be done reliably.
C) Securities rating firms generally do not operate in Europe.
D) Eurobonds are rated by the European financial markets and,therefore,rating by security rating firms is not necessary.