Question 15: Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions: We have practiced (A) exhausting research (B)into the effects of smartphones on students’ (C) behavior and their (D) academic performance

exhaustive (adj): including everything possible; very thorough or complete: comprehensive in all aspects

+ exhaustive research: comprehensive research

exhausting (adj): exhausting, exhausting

academic performance (n, p): academic achievement

Hence: exhausting => exhaustive

“We conducted comprehensive research on the influence of smartphones on student behavior and academic performance.”