Mc Leery is described as the invigilator who had been appointed by the Governor to invigilate. Let's explore this answer in detail:

Introduction:
Mc Leery is a character mentioned in a certain context, and it is important to understand the significance of this character in relation to the given options. The correct answer, option D, states that Mc Leery was the invigilator appointed by the Governor. To understand this better, let's break down the given options and analyze each one.

Options:
a) Evan's friend: This option suggests that Mc Leery was Evan's friend. However, there is no information given in the question to support this option. Therefore, it can be ruled out as the correct answer.

b) Policeman: This option suggests that Mc Leery was a policeman. Again, there is no information provided in the question to support this option. Hence, it can be eliminated as the correct answer.

c) Inspector: This option states that Mc Leery was an inspector. However, just like the previous options, there is no evidence given in the question to support this answer. Therefore, it can be discarded as the correct answer.

d) The invigilator who had been appointed by the Governor to invigilate: This option aligns with the information provided in the question. It mentions that Mc Leery was the invigilator appointed by the Governor. This suggests that Mc Leery was responsible for supervising and monitoring an examination or test. As this option is supported by the given information, it can be considered as the correct answer.

Conclusion:
Based on the information provided in the question, option D stating that Mc Leery was the invigilator appointed by the Governor is the correct answer. The other options, including Evan's friend, policeman, and inspector, do not have any supporting evidence in the given context.