Meter-Yard Stick- And etc
A is an example of direct characterization
It is first person because the author said, "So then I understood," which shows the author is in the situation.
I believe the correct answer is exercitui.
You need the perfect passive form here, which is formed when you combine the verb esse in the present tense (here, sunt because of third person plural), and the appropriate participle in the same person, which in this case is exercitui - third person plural.
