简单随机抽样的布点方便,样地定位不易,在总体内样地分布不均匀。
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If a centrifugal bilge pump were continually operated with the discharge valve closed the ().
A. motor overload would open
B. relief valve would open
C. pump would eventually overheat
D. motor would overheat
在我国教育发展过程中,获取知识和技能的学习方法主要有()、()、()等。
We are disappointed to find that the quality of the products here()very poor.
A. to be
B. have been
C. is
D. being
卫生防疫站调拨生物制品和药械,可按()的增值税征收率征收增值税。