n #$24$ of $25$

Which of the following statements about the first$-$in$,$ first$-$out $($FIFO$)$ inventory cost flow method is true?

a$.$ The first units purchased are assumed to be sold, and the ending inventory is made up of the most recent purchases.

b$.$ The units purchased in the middle of the year are assumed to be sold, and the ending inventory is made up of the other purchases.

c$.$ The cost of the units sold and in ending inventory is an average of the purchase costs.

d$.$ The last units purchased are assumed to be sold, and the ending inventory is made up of the first purchases.