We can't afford to make any mistakes. To us, _______________.
A:a miss is as good as a mile
B:the grass is greener on the other side
C:it never rains but it pours
D:when in Rome, do as the Romans do
有四段导线,甲、乙、丙都是铜线,丁是镍铬合金线,甲与乙等长而甲比乙粗,乙与丙等粗而乙比丙短,丙与丁等长且等粗.关于它们的电阻,下列判断中正确的是( )
下列图案中,轴对称图形的个数是( )