Answer:
No, the given sequence is not arithmetic.
Step-by-step explanation:
The given sequence is

The first term is 5.
A sequence is an arithmetic, if the difference between any two consecutive terms are same.
The difference between terms are



Since the difference between consecutive terms are not same, therefore given sequence is not arithmetic.
Answer: C. 461
Step-by-step explanation:
We know that the formula to find the sample size is given by :-

, where
= Population standard deviation from prior study.
E = margin of error.
z* = Critical value.
As per given , we have
E= 15
Significance level : 
Critical value (Two tailed)=
Now , Required sample size = 
[Round to next integer]
Hence, the required sample size to be taken is 461.
Correct answer = C. 461