Materials are（）.
A.the matter of the universe
B.these substances having properties that make them useful in structures and machines
C.these substances having properties that make them useful in products and systems
D.these substances having properties that make them useful in structures, machines,
devices, products, and systems.
正确答案：the matter of the universe；these substances having properties that make them useful in structures, machines,
devices, products, and systems.