对清洗井底有实际意义的是冲击压力的（）。
A、均匀性
B、非均匀性
C、对称性
D、非对称性
参考答案：B
She decided to combine her new idea __________ she gained watching the black dancing in the
street with the original one.[ ]
A. what
B. where
C. from which
D. which
