【简答题】薄层色谱常用的载体有______或金属片。
【单选题】国家规定的各类经济法主体的义务,对于有关经济法主体来说,都是( )履行的。
【单选题】国家规定的各类经济法主体的义务,对于有关经济法主体来说,都是( )履行的。
【单选题】Consider two copper wires. One has twice the cross-sectional area of the other. How do the resistances of these two wires compare?
A.
Both wires have the same resistance.
B.
The thicker wire has half the resistance of the shorter wire.
C.
The thicker wire has twice the resistance of the shorter wire.
D.
none of the given answers
【单选题】电动机输出转矩方向与转速方向()时称为拖动,()时称为制动