When using a mechanical(windup type)marine chronometer，how often should it be reset ().
A. Only when it is overhauled
B. Whenever the chronometer error exceeds approximately four minutes
C. At the start of each voyage
D. At the start of each voyage
E. If the chronometer rate changes from gaining to losing or vice versa
当测定硬度时，存在Al3+干扰，选择()消除干扰。
A. 控制溶液的PH值
B. 络合掩蔽法
C. 氧化还原掩蔽法
D. 沉淀掩蔽法
易地扶贫搬迁分散安置建房补助标准()
A. 1万
B. 1.5万元
C. 2万元
D. 2.5万元
打接地体时，接地体顶端离地面深度一般不得小于()m。
A. 0.5
B. 0.6
C. 0.7
D. 0.8
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