Correct Option: A

blunt (Adjective) : without a sharp edge or point; very direct
keen (Adjective) : wanting to do something; wanting something to happen very much; eager; sharp; enthusiastic; liking something foolish (Adjective) : silly; stupid
insipid (Adjective) : having almost no taste or flavour; flavourless; not interesting or exciting; dull
plain (Adjective) : easy to see or understand; clear