Mark the variety of iron which has highest melting point

The form of iron having the highest carbon content is

Which of the following statements concern with transition metals ?

The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why ?

Write a note on oxides and oxoanions of transition elements.

Four successive members of the first row transition elements are listed below with their atomic numbers. Which one of them is expected to have the highest third ionization enthalpy