Chemistry - Solid State Question with Solution | TestHub

FCC (face-centered cubic) and HCP (hexagonal close-packed) are closest packing structures. Both have a maximum packing efficiency of about 74%. So, they leave the least empty space (void fraction is minimum).

BCC has lower packing efficiency ($\approx 68\%$), so it has more void space than FCC/HCP. Simple cubic has the lowest packing efficiency ($\approx 52\%$), so it has maximum void space.

Hence, the correct answer is: (B) FCC and (C) HCP.