The question involves determining the order of melting points for pairs of elements (Mn, Fe), (Tc, Ru), and (Re, Os). We have four options to consider. Let's analyze each pair:
Based on the analysis, the correct order of the melting points is Mn < Fe, Tc < Ru and Re < Os.
This corresponds to the correct option given: Mn < Fe, Tc < Ru and Re < Os