10. Mary demanded that he _____ the books he borrowed from her a month ago.
A、 return
B、would return
C、 returned
D、had returned
19. Natural gas can serve as an _____to coal and oil because it is more environmentally friendly.
A、option
B、extra
C、addition
D、alternative
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.( )