生态系统中的生产者指的是( )
A.人类
B.绿色植物
C.动物
D.微生物
参考答案:B
Is this research centre _____ is full of modern equipment you always mention. [ ]
A. where
B. that
C. the one that
D. the one where
某钢筋20(HPB235),其计算简图图示,试计算下料长度为()