以下哪一种结构不属于空间结构体系( )。
A．折板
B．簿壳
C．网架结构
D．屋架
参考答案：D
I ____________ a new crayon.[ ]
A. have
B. is
C. are
The work he devoted his time to _____ worth praising.
A．was
B．be
C．being
D．been
