15 points {= which sentence best shows correct comma usage?
a. corn, cotton fruit wheat beans coffee tomatoes, and rice are grown in mexico.
b. corn, cotton, fruit, wheat, beans, coffee, tomatoes, and rice are grown in mexico.
c. corn, cotton, fruit, wheat, beans, coffee, tomatoes and rice are grown in mexico.
d. corn, cotton, fruit, wheat beans, coffee tomatoes, and rice are grown in mexico.