Option B is correct because the suffix -ful transforms it to an adjective, meaning 'full of'. In the sentence "She had a playful gleam in her eyes", the adjective 'playful' modifies the noun 'gleam'. Option D is correct as the suffix '-able' attributes the meaning 'capable of' to the noun 'play'. In "This ground is playable for a game of football", the adjective 'playable' modifies the noun 'ground'. The words 'playless' and 'playly' do not exist in the dictionary, they're not used in Standard English, hence options A and C are incorrect.