Correct Option: A

clear (Adjective) : easy to see or understand
obscure (Adjective) : not well– known ; unknown ; difficult to understand
bright (Adjective) : full of light ; shining strongly ; strong and easy to see ; cheerful and lively ; intelligent ; quick to learn
open (Adjective) : not closed ; spread out ; not blocked by anything
frank (Adjective) : honest and direct in what you say