Question #N589

Which of the following sentences correctly uses commas to separate items in a series?
A. The recipe calls for flour, sugar, and salt, but I only have flour and sugar.
B. The recipe calls for flour sugar, and salt, but I only have flour and sugar.
C. The recipe calls for flour, sugar and salt, but I only have flour and sugar.
D. The recipe calls for flour, sugar, and salt but I only have flour and sugar.