中国大学MOOC: when a bar of iron attracts other pieces of iron，it ____a magnet，and thus the attraction is called mangnetism.
举一反三
- when a bar of iron attracts other pieces of iron，it ____a magnet，and thus the attraction is called mangnetism. A: will be acted as B: acts as C: is acted as D: has been acted as
- The period during (when) people (learned to) smelt iron is (called) (the) Iron Age. A: when B: learned to C: called D: the
- n. a piece of iron that attracts objects made of iron towards it, either naturally or because of an electric current that is passed through it A: manual B: layout C: jungle D: magnet
- At the top of the A-frames there is a strong cast iron frame called （）.
- In addition to iron and carbon, list the other elements that may be found in a grey cast iron and describe their effect on the properties of a grey cast iron.