The correct answer is A. Server.
A server is a computer that is used to provide services to other computers. In the context of the question, a server is a computer that serves webpages. This means that it is responsible for storing and delivering webpages to users.
A host is a computer that is connected to a network and can be accessed by other computers on the network. In the context of the question, a host is a computer that is used to store and deliver webpages. However, it is not the computer that is responsible for serving the webpages to users.
A client is a computer that is used to access resources on a network. In the context of the question, a client is a computer that is used to access webpages. However, it is not the computer that is responsible for storing or delivering the webpages.
A router is a device that is used to connect two or more networks. In the context of the question, a router is not directly involved in the storage or delivery of webpages.
I hope this helps! Let me know if you have any other questions.