用方框中所给的单词填空，使对话通顺、正确.

fingers,  need,  when,  round,  fast

Do you know how blueberries grow? They grow on bushes. Each blueberry is small and
  . Many blueberries can grow on one bush. At first, the blueberries are green. The green blueberries are not ready to eat. They      a lot of sun and rain to help them become big and sweet.      they turn blue, people can pick them.
Some farmers grow blueberries in big fields. The people nearby can make money by helping to pick the blueberries. They work      so that they can pick up more blueberries. While they are picking blueberries, their       are blue because of the juice of the berries.