Primitive Solid

After building your time machine, you set it to 30,000 BCE to observe saber-toothed cats. However, a glitch in the software programmed by Monkton Tuesdale sent you back to only 300 BCE. Now that you are alone in ancient Greece, you don't dare use the time machine again until you fix the code.

You found the leading mathematician of the time, Euclid, and asked for his help. He has agreed to help you only if he deems that you are worthy. He needs only one question to determine this. If you can answer this question correctly, he will help you and you can get back to exploring time.

Question:  The three primitives of geometry that Euclid defined are the point, the line and the plane. These correspond to the dimensions zero, one and two. Which of the following solids is the only logical choice for a three-dimensional primitive given the progression from point to line to plane:

a) sphere
b) tetrahedron
c) cube
d) octahedron
e) dodecahedron
f) icosahedron

Good luck!