Нужно поставить прилагательные в сравнительную или превосходную степень.
This is Tony Pratt and his sister, Fiona. Tony is taller than Fiona. but she is older than him. She is the older student in her class. They both like running, but Tony is the fastest boy in their school. Sometimes they argue, but Tony thinks Fiona is the best sister in the world.
Ответ: taller, older, fastest, best.