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Generally, 3d transition metals have high melting points.
Reason: Involvement of 3d-electrons in addition to 4s-electrons in the interatomic metallic bonding.
Detailed Solution
In d-block metals, unpaired electrons of the (n-1)d subshell also take part in metallic bonding along with the ns electrons. This makes interatomic metallic bonding comparatively strong, hence their melting points are high. Both A and R are correct and R explains A.