8
5
1
3
Answer is Right!
Answer is Wrong!
The answer is $\boxed{3}$.
The missing number is the number that completes the sequence $1, 3, 5, 7, \boxed{?}$. This is an arithmetic sequence with a common difference of $2$. Therefore, the missing number is $1 + 2 = \boxed{3}$.
Option A is incorrect because $8$ is not a term in the sequence.
Option B is incorrect because $5$ is already a term in the sequence.
Option C is incorrect because $1$ is the first term in the sequence.
Option D is incorrect because $7$ is the fourth term in the sequence.