混纺纱
参考答案：
是由两种或两种以上不同种类纤维纺制而成的。
China is the third ______ country in the world. [ ]
A. large
B. largest
C. larger
D. as large as
为了防止铜及铜合金焊接时产生冷裂纹，焊前工件常需要预热。( )
