The correct answer is A. Transition metals.
Transition metals are elements in the d-block of the periodic table. They are characterized by having partially filled d-orbitals. Iron (Fe), cobalt (Co), and nickel (Ni) are all transition metals.
Main group metals are elements in the s-block and p-block of the periodic table. They are characterized by having a full valence shell of electrons. Examples of main group metals include sodium (Na), potassium (K), and magnesium (Mg).
Alkali metals are elements in the first column of the periodic table. They are characterized by having one valence electron and a very low ionization energy. Examples of alkali metals include lithium (Li), sodium (Na), and potassium (K).
Rare metals are elements that are relatively scarce in the Earth’s crust. Examples of rare metals include platinum (Pt), rhodium (Rh), and palladium (Pd).
In conclusion, the group of metals Fe, Co, Ni may best called as transition metals.