One Question Per Page false false Which one of the pair is a past tense? 2 Which one of the pair is a future possibility? 2 Which one of the pair is an ability at a given time? 1 Which one of the pair is more formal and polite? 2 Which one of the pair describes permission? 1 https://339efcb25eb75e967b0d-ff8eeadd950d51fd1fc939dca75b3973.ssl.cf1.rackcdn.com/assets_green.swf