The correct answer is: C. both local memory and clock
A distributed system is a collection of autonomous computers that work together to solve a common problem. Each computer in a distributed system has its own local memory, which is used to store data and programs that are specific to that computer. Each computer also has its own clock, which is used to keep track of time.
Local memory is important because it allows each computer to store data and programs that are specific to that computer. This can improve performance, as it means that the computer does not have to access data or programs that are stored on another computer.
A clock is important because it allows each computer to keep track of time. This is important for tasks such as scheduling and synchronization.
Option A is incorrect because not all distributed systems have local memory. For example, in a peer-to-peer network, each computer can access the data and programs that are stored on any other computer in the network.
Option B is incorrect because not all distributed systems have clocks. For example, in a time-slotted network, each computer is assigned a time slot in which it can access the network. This means that the computers do not need to have their own clocks.
Option D is incorrect because both local memory and clocks are important in distributed systems.