Answer:
○ communication
Step-by-step explanation:
An abstract noun is a noun which denotes an idea or quality rather than an actual object.
Using this definition, we can see that 'communication' is the abstract noun here, because it relates the idea of exchanging information, and is not an actual, tangible thing.
• The other options, website, letter and telephone are all actual objects and not ideas, therefore they are not abstract nouns.