[单选题]钢筋焊接作业完毕后应（　　），检查现场，确认无火灾隐患后方可离开。
A.切断电源
B.拆除接地
C.拆除护栏
D.悬挂标示牌

Of 2, 000 commercial beekeepers in the United States about half migrate. Migratory beekeeping is nothing new. The ancient Egyptians moved clay hives, probably on rafts, down the Nile to follow the bloom and nectar flow as it moved toward Cairo. In the 1880s North American beekeepers experimented with the same idea. moving bees on barges along the Mississippi lighter, wooden hives kept falling into the water, Other keepers tried the railroad and horse drawn wagons, but that didn’t prove practical. Not until the 1920s when cars and trucks became affordable and roads improved, did migratory beekeeping begin to catch on.
For the Californian beekeeper, the pollination season begins in February. At this time. the beehives are in particular demand by farmers who have almond groves; they need two hives an acre. For the three-week long bloom, beekeepers can hire out their hives for $ 32 each.
By early March it is time t