Mark the letter A, B, C, or D on your answer sheet to indicate the word that differs from the other three in the position of primary stress in each of the following questions. 

A. purchase

Đáp án D

A. purchase /'pз:tʃǝs/

B. ladder /'lædǝ(r)/

C. forest /'forɪst/

D. police /pǝ'li:s/