Answer:
C. work backwards
Explanation:
Given from the first statement of the question that that four people are in line. This is the result of the question, so the strategy required would be the work backwards.
Jennifer is ahead of Jeanie implies that Jeanie is somewhere behind Jennifer. Since John is neither the first or the last in the line, then he must be between Jeanie and Jennifer. And Jarett is directly in front of Jennifer, so that Jarett is the first in line. The arrangement goes thus:
Jeanie ⇒ John ⇒ Jennifer ⇒ Jarett