Answer:
b)starts at zero at the beginning of the first period and then increases by a constant amount each period.
Step-by-step explanation:
A series is called arithmetic gradient series if it increases or decreases periodically by a constant amount.
Examples are
0,.100,200,300, 400 ....
Decreasing series would be
1000, 800, 600., 400....
Thus the difference between the consecutive terms is a constant.
Hence here out of four definitions we find that
b)starts at zero at the beginning of the first period and then increases by a constant amount each period.