Since fuse elements are made of zinc or any alloy of tin and lead, the melting point of the fuse element must be ().
A. higher than that of copper
B. lower than that of copper
C. equal to that of copper
D. reached when the conductor it is protecting becomes "white hot"
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自然资源和()的重要区域以及珍稀动物和植物基因的资源保护地带,都属于禁止开发区。
跳汰洗煤时,增大跳汰机筛孔的孔径能加强()。
A. 吸啜作用
B. 床层稳定
C. 透筛排料
D. 煤量给入