The correct option is
C Triangular shape empty spaces or voids are present in hcp
Hexagonal close packing in 2-D
Here, the second row of spheres is placed in the interstices or depressions of the first-row spheres. Thus, it gives ABAB... type arrangement.
In this arrangement some triangular shaped, empty spaces are present. These are called triangular voids.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1106876/original_1.PNG)
Each sphere touches 6 other neighbours. Thus, its coordination number is 6.
The centres of the neighboring spheres join to form a hexagon. So, the packing is known as hexagonal close packing in 2-D.
Thus, statement (a), (b) and (c) are correct.