问题
选择题
There is _______ "u" and _______ "s" in the word “useful”. [ ]
A. an, a
B. a, an
C. a, a
D. an, an
答案
答案：B
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There is _______ "u" and _______ "s" in the word “useful”. [ ]
A. an, a
B. a, an
C. a, a
D. an, an
答案：B
试求在(0，+∞)内连续的函数y=y(x)，使之在(0，1)和(1，+∞)内都满足所给方程且