Which answer best describes an advantage to a planarian worm from having a high stem cell count?

a
a planarian worm's cells can never truly die
b
planarian worms can adapt to any environmental changes
c
planarian worms are able to evolve faster than other organisms
d
a whole new planarian worm can grow from a tiny piece of another

d) a whole new planarian worm can grow from a tiny piece of another