Final answer:
The provided excerpts do not depict Nurse Ratched's reason for McMurphy's presence at the ward. In 'One Flew Over the Cuckoo's Nest,' Nurse Ratched believes McMurphy feigns insanity.
Step-by-step explanation:
The dialogue excerpts provided do not directly disclose how Nurse Ratched explains McMurphy's reason for being at the ward. Instead, the excerpts feature various nurses in different contexts talking about their experiences, their decisions, and the patients they care for.
However, to provide an answer based on the widely known novel 'One Flew Over the Cuckoo's Nest' by Ken Kesey, Nurse Ratched explains McMurphy's presence in the psychiatric ward by stating that he is a manipulative individual who is pretending to be insane in order to escape the hard labor of the prison work farm.