The phrase that best summarizes the theory of evolution by natural selection is B) only the strongest animals survive. If you are strong enough and can fight for survival, you are more likely to survive than some other creature that doesn't know what to do to make a living.
IT IS NOT POSSIBLE to produce malleable cast iron in pieces having large cross sectional dimension. This is because, iron has a very rapid cooling rate and it will not be possible to achieve this rate at different cross sectional areas in a sheet of iron.