Which of the following options are correct?

Correct statements are(a) Cast iron is obtained by remelting pig iron with scrap iron and coke using hot air blast.(d) Zr and Ti are purified by van-Arkel method as,Zr Impure +2I2⟶ZrI4 Volatile ⟶ΔZr+2I2 Pure (b) and (c) can be correctly stated as(b) In extraction of silver, silver is extracted as anionic complex Ag(CN)2(c) Nickel is purified by vapour phase refining method.       Ni+4CO⟶330−350KNi(CO)4⟶450−470KNi+4CO