A charge +q is brought near an isolated metal cube having no charge initially

cube becomes positively charged. cube becomes negatively charged. external surface becomes negatively charged and interior becomes positively charged. Interior remains charge free and the surface gets non-uniform charge distribution.

Interior remains charge free and the surface gets non-uniform charge distribution.

Due to charge +q negative charge will be induced on the surface near to the external charge. Positive charge will shift on the other side of the cube.  Being metal conductor, the interior will remain charge free. ∴ (D)