Решение:
Заполняем пропуски предлогами 'apart', 'behind' или 'out':
- 28. Julie fell out with her brother because he wasn't nice to her. ('Fall out with someone' - поссориться с кем-либо).
- 29. This book is falling apart. I have to buy a new one. ('Fall apart' - разваливаться, приходить в негодность).
- 30. He fell behind in his work because he was on holiday. ('Fall behind' - отставать в работе/учебе).
Ответ: 28. out, 29. apart, 30. behind.