单项选择题

By immersing ore particles in water, ______.

A．we can get ore particles of equal size
B．we can purify aluminum particles
C．we can filter out aluminum
D．we can improve the working conditions around

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热门试题

单项选择题

It is believed that a new technique to ______ will probably be found.

A．recycle old aluminum products
B．discover more bauxite ores
C．make aluminum by putting ore particles under water
D．take out aluminum magnetically from poorer ores

单项选择题

In the second paragraph the word paramagnetic means ______.

A．slightly magnetic
B．a weak magnetic field
C．a strong magnetic substance
D．the under-water magnetic power