Question 446057
It is possible for a pentagon to tessellate a plane. Draw a "house" shaped pentagon:

{{{drawing(200,200,0,10,0,10,

line(2,2,8,2),
line(8,2,8,5),
line(8,5,5,8),
line(5,8,2,5),
line(2,5,2,2)

)
}}}

Place several of these side by side, same orientation, then reflect the pentagon to tessellate the plane. Given this, we know that statements a and c need not be true.

The ability to tessellate the plane was not dependent on the sides being the same length either, so choice b is not true either. This leaves the only remaining choice, d.

A greater challenge: Can you prove that statement d must be true, without using process of elimination?