$\begin{array}{1 1}(a)\;\text{Due to }d^1\text{ configuration, metallic bonds are strong}\\(b)\;\text{Due to }d^5\text{ configuration, metallic bonds are weak}\\(c)\;\text{Due to }d^7\text{ configuration, metallic bonds are weak
}\\(d)\;\text{None of these}\end{array}$
