材料不管是自然状态还是绝对密实状态，其体积总是相同的。
参考答案：错
As many as 100 species of fish, some ____ to these waters, may have been affected by the pollution．
A．relevant
B．immune
C．unique
D．convenient
简述普通磨料砂轮和超硬磨料砂轮在修整机理上的不同。
