导线的选择主要是选择导线的种类和导线的截面。
参考答案：对
Nowadays, the iron and steel industry _____ the key link in socialist production. [ ]
A. is
B. are
C. was
D. were
( )降解酶较少，有可能是蛋白质多肽类药物吸收较理想的部位。
A．胃B．小肠C．结肠D．直肠E．十二指肠
