对锚具的要求是安全可靠、使用有效、节约钢材及制作简单。 ()
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部分预应力混凝土是在使用荷载作用下截面混凝土不允许出现拉应力。()
A. 对
B. 错
后张法是在浇筑混凝土并结硬之后张拉预应力筋。()
A. 对
B. 错
先张法是在浇筑混凝土之前张拉预应力筋。 ()
A. 对
B. 错
U1R1 P1:Droughts and forest fires have been occurring dramatically more often in the past century.近百年来,干旱和森林火灾的爆发愈加频繁。U1R4 P1:Forecasting climate change is extremely difficult, but the evidence is now irrefutable: human activities are driving the current period of global warming.气候变化难以预测,但证据却是无可辩驳的存在:人类活动正在推动当前的全球变暖现象。There are many predictions, but ____________________: ____________________(不可辩驳的事实是:干旱比起往年频繁出现)