MFE Sample 61

In the solutions of Sample 61, we are told to use this to solve the problem:

E*[Z squiggle(t)] = 0.
It says this is in Section 20.5 of McDonald 2006, page 662.

I am using the Third Edition, and do not believe the explanation is in the same place as in the 2006 edition. Can someone guide me to where I can find this explanation, or explain to me why it's equal to 0?

THanks,


MFE Sample 61