LITA is not a ChatClient
Option (b) Lita is correct answer here
Chat client are referred as a special type of software which is located in the computers of the user's for handling of instant messaging (IM) from other users or use in chat rooms.
Chat Client are used for the reading of instant messages and chat. A chat bot is another computer program which can simulate human interface through voice or commands messages in the form of text chats.
Chatbot, or called as chatterbot, is a kind of Artificial Intelligence (AI) tools which can be embedded and utilized through any major messenger type applications.
Example of ChatClient are Flowdock,HipChat and Campfire.