The correct answer is D. OFDMA.
CDMA2000 is a 3rd generation (3G) cellular technology that was developed by the Third Generation Partnership Project (3GPP). It is a direct descendant of the second generation (2G) CDMA technology, and it is designed to provide higher data rates and capacity than 2G systems.
CDMA2000 uses a number of different features to achieve its performance goals. One of these features is adaptable baseband signalling rates. This means that the system can adjust the rate at which data is transmitted based on the available bandwidth and the quality of the radio link. This allows CDMA2000 to provide a consistent user experience even in areas with poor signal strength.
Another feature of CDMA2000 is adaptable baseband chipping rates. This means that the system can adjust the rate at which data is scrambled based on the available bandwidth and the quality of the radio link. This allows CDMA2000 to provide a higher level of security than other 3G technologies.
CDMA2000 also uses multicarrier technologies. This means that it can divide the available bandwidth into multiple smaller channels, which can then be used to transmit data from multiple users simultaneously. This allows CDMA2000 to achieve higher data rates and capacity than other 3G technologies.
OFDMA is a different type of multicarrier technology that is used in some 4G LTE systems. It is not a characteristic of CDMA2000.