Which of the following is a back vowel？
A. [i:]
B. [i]
C. [a]
D. [u]
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Among the following sounds, ______is a voiceless alveolar fricative.
A. [z]
B. [s]
C. [f]
D. [v]
乘坐国内航线旅游时，已满2周岁未满12周岁的儿童按成人票_____付费。
Which of the following italicized parts is an inflectional morpheme？(2013)
A. Unlock
B. Government
C. Goes
D. Off-stage
美国药典的英文缩写为()
A. USP
B. GMP
C. BP
D. JP
E. WHO
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