The question asks to identify an arithmetic sequence with a common difference of 4. Let's analyze the given options:

1. 2, 8, 32, 128, 512, ...
   This is a geometric sequence because the ratio between consecutive terms is not constant addition but rather multiplication (e.g., $8 \div 2 = 4$).

2. 4, 6, 8, 10, 12, ...
   This sequence has a common difference of $2$, not $4$.

3. 4, 8, 16, 32, 64, ...
   This is also a geometric sequence since each term is multiplied by $2$.

4. 5, 9, 13, 17, 21, ...
   This is an arithmetic sequence, and the common difference is $9 - 5 = 4$.

Correct Answer: 5, 9, 13, 17, 21, ...

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Five Related Questions:

1. What is the formula for the nth term of an arithmetic sequence?
2. How can you identify a geometric sequence from its terms?
3. What are the differences between arithmetic and geometric sequences?
4. How do you calculate the sum of an arithmetic sequence?
5. What real-world scenarios use arithmetic sequences?

Tip:

In an arithmetic sequence, always check the difference between consecutive terms—it must remain constant.