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 identify the one that is different from the others in pronunciation. Mark your answer by blackening the corresponding letter on the Answer Sheet.1.( )
A、cake
B、gas
C、bag
D、tax
7. By the time he retires, Carl _____ president for 15 years at the university.
A、would be
B、will have been
C、will be
D、 has been
52. What is the main reason for reducing salt in food?