Answer:
The last answer, "Four groups of four soldiers watched over Peter/in jail."
Explanation:
Predicate : the part of a sentence or clause containing a verb and stating something about the subject (e.g., went home in John went home ).
("in jail")
Subject : a person or thing that is being discussed, described, or dealt with.
"I've said all there is to be said on the subject"
("Peter")