L3R11.h foreign exchange and bond riskiness

Can someone explain to me why bond in country C is preferred.

solution says

Many emerging market bonds are denominated in a hard currency, so less risky countries have greater foreign currency reserves.

I don’t understand the link between hard currency and foreign currency reserve and how they translate into more desirable bond. I assume it is to do with less bond risk of country C given the two measurements in the table.