Explanation:
To find the 31st term of the arithmetic sequence \(1, 4, 7, 10, \ldots\), follow these steps:

1. Identify the first term (\(a\)) and the common difference (\(d\)) of the sequence:

- First term \(a = 1\)
- Common difference \(d = 4 - 1 = 3\)

2. Use the formula for the \(n\)-th term of an arithmetic sequence:

\[
a_n = a + (n - 1)d
\]

Here, \(n = 31\), \(a = 1\), and \(d = 3\).

3. Substitute these values into the formula:

\[
a_{31} = 1 + (31 - 1) \times 3
\]

\[
a_{31} = 1 + 30 \times 3
\]

\[
a_{31} = 1 + 90
\]

\[
a_{31} = 91
\]

Thus, the 31st term of the sequence is:

B. 91