Which of these best describes the composition of white cast iron?
a) iron-carbon alloy with between 2.5 and 4.0 wt% carbon and less than 1.0 wt% of silicon
b) iron-carbon alloy with between 2.5 and 4.0 wt% carbon and between 1.0 and 3.0 wt% of silicon
c) iron-carbon alloy with normally between 3.1 and 4.0 wt% carbon and between 1.7 and 3.0 wt% of silicon
d) iron-carbon alloy with low carbon content, a little manganese and only residual amounts of other impurities