Use the comma to set of coordinating adjectives

What happens once in a minute twice in a moment and never in a thousand years?

Which excerpt from leo tolstoy's the death of ivan ilyich reflects the author's opinion that the members of the medical profession don't really care about their patients?

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were a 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.