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