3D printers are still _____ expensive for most of us ______ afford. ( )
A:so, to
B:such, to
C:too, to
D:much, to
t℃时,在饱和硫酸铜溶液中加入a g无水硫酸铜,恢复至原温度可析出b g硫酸铜晶体。说法正确的是( )