Ответ:

  1. Lilly gave up fencing two years ago because of a bad injury. Give up means «бросить, прекратить».
  2. Susan gave away her old clothes to charity. Give away means «отдать безвозмездно».
  3. They’re giving away free tickets at the cinema. Give away means «раздавать бесплатно».
  4. I’ll give the keys back to you tomorrow morning. Give back means «вернуть».

Ответ: 1 — up; 2 — away; 3 — away; 4 — back.