You can mark responses as invalid or valid and correct responses from the Chat Logs page under Admin. You can also view all of your bot's learned responses and edit them.
If you mark those two responses as invalid, then your bot will use the third response.
If you create your bot using the default template it will contain at "WhatIs" script that attempts to answer "what is" type questions. You can delete this script from the Program page under Admin.
If you are making a bot for a specific purpose, it is best to delete the "WhatIs" and the "NounVerbAdjectiveStateMachine" scripts, or start with an empty template.