Answer:
Option B
Explanation:
The correct order of densities of d- block elements are as follows:
Ni > Fe > Cr > V
On moving across a period electrons have the same principal quantum number and so they are not making the atom bigger, but at the same time there is more protons and neutrons resulting increase in the number of nuclei and due to an effective increase in charge of the nucleus there is decreases in a radius of the atom.
$density =\frac{mass}{volume}$
mass is increasing and volume is decreasing, overall we conclude that on moving left to right density increases
