由于铜具有良好的导热性能，不易使局部加热，因而铜管的可焊性较差。( )
参考答案：对
生铁的磅差允许（）‰。
A、5%
B、2%
C、1%
D、5%
The （）shoes were covered with mud, so I asked them to take them off before they got into （）car.
A. girl' s ; Tom' s
B. girls' ; Toms'
C. girls' ; Tom' s
D. girl' s ; Toms'
