Practical Geometry Symmetry & Visualising Solid Shapes

If three cubes each of edge 4 cm are placed end to end, then the
dimensions of resulting solid are:
(a) 12 cm × 4 cm × 4 cm (b) 4 cm × 8 cm × 4 cm
(c) 4 cm × 8 cm × 12 cm (d) 4 cm × 6 cm × 8 cm