Explanation:

A. Dilligent: The correct spelling of this word is 'diligent', with a single 'l'. Therefore, 'Dilligent' is misspelt.\nB. Diaspora: This word is correctly spelt. It refers to the dispersion of any people from their original homeland.\nC. Conspicuous: This word is correctly spelt. It means standing out so as to be clearly visible, or attracting attention.\nD. Abysmal: This word is correctly spelt. It means extremely bad; appalling.