屋顶钢架、大桥钢架多采用三角形结构,这是根据______.
屋顶钢架、大桥钢架多采用三角形结构,这是根据三角形具有稳定性.
故答案为:三角形具有稳定性.
(7分)如图,将铜片和锌片焊接在一起组成A电极,B为碳棒进行电解实验,电解液中含硝酸银和硝酸铜各0.1 mol。已知电路中通过0.2 mol电子。
(1)请写出A.B两极发生反应的电极反应式A: B:
(2)请分析A.B两极质量变化情况为A:___________B:__________
There ____ a table, four chairs, three bikes in the courtyard, in the middle of which ____ two tall trees with great shade.
A.are; is
B.is; are
C.has; have
D.have; has