'A Different World' is a spin-off of which TV series?

'That '90s Show' is a spin-off of which TV series? 'House of the Dragon' is a spin-off of which TV series? 'Melrose Place' is a spin-off of which TV series? 'Trapper John, M.D.' is a spin-off of which TV series? 'The Conners' is a spin-off of which TV series? 'Family Matters' is a spin-off of which TV series? 'Benson' is a spin-off of which TV series? 'Torchwood' is a spin-off of which TV series?