单项选择题
A.It is strong. B.It conducts heat well. C.It weighs little. D.It is inexpensive to produce.
A.The development of insulation materials. B.Increased airplane production. C.Improved medical facilities. D.The development of the cheap inks for printing.
A.Use of sea water. B.Treatment of sea water. C.Chemical properties of magnesium. D.Derivation and users of magnesium.