Space lattice of \(CaF_2\) is:

body centred cubic

The answer is 3. body centered cubic.

The space lattice of \(CaF_2\) is body centered cubic (bcc). In this structure, each atom is surrounded by 8 other atoms, located at the corners of a cube and at the center of the cube.

Here is a diagram of the \(CaF_2\) crystal structure:

The blue spheres represent calcium atoms and the green spheres represent fluorine atoms. As you can see, each calcium atom is surrounded by 8 fluorine atoms, and each fluorine atom is surrounded by 8 calcium atoms.

The other three options are incorrect. A simple cubic lattice has only one atom per unit cell. A face-centered cubic lattice has 8 atoms per unit cell. A hexagonal closed packed lattice has 12 atoms per unit cell.