Answer

Packing fraction for the cubic unit cell is given by:

Packing efficiency of simple cubic is π/6 or 0.52.
That means, 48% is empty and 52% is occupied.
Hence, option (3) is incorrect, whereas all other options are correct.
In the diamond crystal carbon atoms and are arranged in the face centered cubic crystal structure. Hence, Z = 4.
There are a total of 14 types of crystal lattices.
In a simple cubic unit cell the atoms are present only at the corners and Z = 1.