问题
选择题
Maths ____ one of the ____ subjects in middle school. [ ]
A. are; important
B. is; most important
C. is; more important
D. are; much important
答案
答案：B
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Maths ____ one of the ____ subjects in middle school. [ ]
A. are; important
B. is; most important
C. is; more important
D. are; much important
答案：B
的时间，这列波恰好第三次重复出现图示的波形。
时刻的波形。