问题
选择题
There _____ a pen and two rulers in my pencil case. [ ]
A. are
B. be
C. is
D. am
答案
答案：C
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There _____ a pen and two rulers in my pencil case. [ ]
A. are
B. be
C. is
D. am
答案：C
与C8H6互为同分异构体