I believe it’s B have a great day
Answer:
The third option.
Step-by-step explanation:

Hence the 3rd option.
Looks like you just evaluated the summand for the given value of

, whereas the question is asking you to find the value of the sum for the first

terms.
Let

. Then

is the

th partial sum.

happens to be the first term in the series, which is why that box is marked correct:

But the next partial sum is not correct:

and this is not the same notion as the second term (which indeed is 0.75) in the series.
A "roster" here is essentially a version of the set with all of elements listed out. Here, those elements are all of the odd numbers between 20 and 30, so our list would be
{21, 23, 25, 27, 29}