Suggested answer for Exercise 4

The sentence in The bird was caught is passive. The main verb takes a theme argument. The v head is occupied by the passive morpheme en, which does not assign accusative Case to the DP in the specifier of the VP and it does not assign an agent thematic role to its own specifier position either. That is why there is no agent argument in this sentence. Since the passive morpheme is a bound morpheme, the main verb has to move to v. The theme DP in the specifier of the VP needs to be assigned Case, so it moves to the specifier of IP in order to receive Case from the finite I. A higher tense vP is also projected where the dummy auxiliary be is inserted to support the bound tense morpheme. At the S-structure the auxiliary moves on to the I head.