Concept:A preposition links a noun or pronoun to another word, often showing origin, time, or relationship.
Explanation:The blank needs a preposition that shows when the friendship began.
"School times" refers to a past period.
"From" is used to indicate the starting point or origin of something.
So "an old friend from school times" means a friend known since school.
The other options do not fit naturally: "to" shows direction, "of" shows possession, and "in" shows location or inclusion.
Answer:The correct preposition is "from".
Complete sentence: She is an old friend from school times.