(1) the leaves scattered across the street like they were playing a game of tag. (2) the wind had just the slightest bite of winter's first chill. (3) the wind calmly came in spurts. (4) duncan raced down the street on his bicycle and his little sister tried hard to keep up.(5) today was the day that mr. carpenter visited the school. (6) he always amazed duncan with his wild science experiments. (7) what duncan did not know was that this day would be different. (8) he was not going to just watch mr. carpenter's science show. (9) he was going to be a part of it.

what change should be made in sentence 4?
a. capitalize sister.
b. add a comma after street.
c. add a comma after bicycle.
d. change raced to racing.