Which sentence below expresses numbers correctly?
a. There were only twenty four desks for the thirty children in Mr. Clark’s morning kindergarten class.
b. The average weight of a chocolate bar was one fourth greater in the sixties than today.
c. Did you know that the earth is 4,500,000,000 years old?
d. “If you 2 don’t settle down right now I am going to turn this car around!” yelled Dad.