The correct answer is: B. GPRS
GPRS (General Packet Radio Service) is a 2.5G mobile technology that provides packet-switched data services on the 2G GSM network. It is not backward compatible with 3G Cdma2000 because it uses a different air interface and different protocols.
IS-95 is a 2G mobile technology that uses CDMA (Code Division Multiple Access) as its air interface. It is available in two versions: IS-95A and IS-95B. IS-95A is the original version, while IS-95B is an enhanced version that offers higher data rates. Both IS-95A and IS-95B are backward compatible with each other.
3G Cdma2000 is a 3G mobile technology that uses CDMA as its air interface. It is available in several versions, including Cdma2000 1xRTT, Cdma2000 EV-DO, and Cdma2000 EV-DV. All versions of 3G Cdma2000 are backward compatible with each other.
In conclusion, GPRS is the only option that has no backward compatibility with 3G Cdma2000.