Which sentence does not contain any errors in comma usage?

a. vanessa whom you don't know, will ride on a float in the parade.
b. bobby thompson, whose middle name is herbert, lives three doors away from us.
c. mrs. fanelli whom we know from our neighborhood can fly airplanes.
d. a famous author, whose name escapes me right now will give a speech at the library.

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.