p. 81 Ex 3 instructions
The instructions say "Draw trees for the sentence below" which implies that more than one tree is possible, but only one tree is possible. This leads to people trying to draw trees for the ungrammatical sentences, which isn't the point of the exercise.
The instructions should also be clearer in stating that people should explain how using the tree how the two ungrammatical examples are ruled out, and the grammatical ones are ruled in.