Query about Question 4 from "(GRE Big Book) Test 1 Text Completion Problems (14)" [9695]

GRE GRE Verbal Problem Solving
1

https://www.gregmat.com/quizzes/quiz/gre-big-book-test-1-text-completion-problems-14 (Question 4)

Can i know what strategy has been used here?

2

How would you solve it?