I.Phonetics ( 5 points)Directions:In each of the following groups of words, there are four underlined letters or letter combinations marked A, B, C and D. Compare the underlined parts and iden-tify the one that is different from the others in pronunciation. Mark your answerby blackening the corresponding letter on the Answer Sheet.
A、 penalty
B、moment
C、quarrel
D、absent
24.
A、 because
B、if
C、while
D、whether
52. What does the underlined word "centenarians" in Paragraph 1 refer to?