80. From the aspect of electromechanics, the automatic doors installed in the convenience stores and modern office building is a device of . (A)sensoring and control (B)electroetching (C)conservation of heat (D)energy generation

59. Which of the following statements about the structure is incorrect？ (A)The arch structure is well stressed, the disadvantage is that it takes up space. (B)The truss structure uses simple materials to withstand weight, and is often used to build bridges. (C)The cable structure is cheap and beautiful, and it is often used as the main structure of the building. (D)The beam-column structure is very stable for building houses, but it takes up space and consumes materials.

80. From the aspect of electromechanics, the automatic doors installed in the convenience stores and modern office building is a device of .
(A)sensoring and control
(B)electroetching
(C)conservation of heat
(D)energy generation

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