The correct answer is D. realtime.
A distributed database system (DDP) is a database management system (DBMS) that distributes data and processing across multiple computers. This allows DDP systems to handle large amounts of data and provide high availability and performance.
There are several different ways to configure a DDP system. The most common configurations are star, ring, tree, and bus.
In a star configuration, each node in the network is connected to a central hub. This is the simplest and most common configuration.
In a ring configuration, each node in the network is connected to two other nodes. This configuration is more fault-tolerant than a star configuration.
In a tree configuration, each node in the network is connected to one or more other nodes. This configuration is more scalable than a star or ring configuration.
In a bus configuration, all nodes in the network are connected to a single bus. This configuration is the least fault-tolerant of the four configurations.
A realtime system is a system that must respond to events within a specified time limit. This is in contrast to a non-realtime system, which can respond to events at any time.
Realtime systems are often used in critical applications such as air traffic control, medical imaging, and manufacturing.
The realtime configuration is not a common configuration used in a DDP system. This is because realtime systems require a high level of reliability and performance, which can be difficult to achieve in a distributed system.