ANS:D - simple cubic

The lowest packing of atoms exists in the simple cubic crystal lattice structure. Explanation:

• In the simple cubic (sc) lattice structure, each atom is located at the corners of a cube, and there is only one atom per lattice point.
• This arrangement results in the least efficient packing of atoms, with only 52.4% of the volume occupied by atoms.
• In contrast, both the face-centered cubic (fcc) and hexagonal close-packed (hcp) structures have higher packing efficiencies, with 74% and 74.05% of the volume occupied by atoms, respectively.
• The body-centered cubic (bcc) structure has a packing efficiency of 68%, which is higher than that of the simple cubic lattice but lower than that of fcc and hcp structures.
• Therefore, the lowest packing of atoms exists in the simple cubic crystal lattice structure.