What____used as chief building materials today____steel and concrete.
A: have been . . . are
B: is . . . are
C: are . . . are
D: are . . . is
A: have been . . . are
B: is . . . are
C: are . . . are
D: are . . . is
举一反三
- 智慧职教: What ___ used as chief building materials today __ steel and concrete.
- Concrete is a polluting material, so all green building materials can be used to replace it. A: 正确 B: 错误
- Engineering materials such as steel and concrete are the basis of construction projects.
- 中国大学MOOC: Concrete is a polluting material, so all green building materials can be used to replace it.
- Under a certain long-term load, concrete would creep. In the reinforced concrete axial compressive members: A: Creep increases the compressive stress of concrete. B: The compressive stress of concrete and steel bar keeps unchanged. C: Creep decreases the compressive stress of concrete and increases the compressive stress of steel bar. D: Creep increases the compressive stress of concrete and decreases the compressive stress of steel bar.