Which of the following is true if a pentagon tessellates a plane?

a. A pentagon never tessellates a plane
b. All of its sides must be the same length
c. It must be a regular pentagon
d. It has one pair of parallel sides

I was thinking its (c) but not sure.

Since this is not my area of expertise, I searched Google under the key words "pentagon tessellates a plane" to get these possible sources:

http://www.google.com/search?client=safari&rls=en&q=pentagon+tessellates+a+plane&ie=UTF-8&oe=UTF-8

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.