变形缝的基层应采用不燃材料，表面层不应采用（）材料。
A、易燃
B、可燃
C、难燃
D、不燃
参考答案：A, B
We don’t have to keep these old chairs any more. ________, they are falling apart（支离破碎）.
A．Therefore
B．However
C．Otherwise
D．Anyway
