Suggested answer for Exercise 2
| a | [S [DPthe postman] [VP lost [DP his key] [DP yesterday]] | |
| b | [S [DP the student [S [DP who] [VP has just passed [DP the exam]]]] [VP is [AP very happy]]] | |
| c | [S [DP this theory [PP of [DP [DP language] acquisition]]] [VP is [AP easy [PP for [DP students [S [DP who] [VP understand [DP mathematics]]]]]]]] |