Step 1: Express terms as products of consecutive integers.
\[
12=3\times4
\]
\[
24=4\times6
\]
\[
48=6\times8
\]
\[
84=7\times12
\]
A more suitable observation is:
\[
12=3\times4,\quad
24=4\times6,\quad
48=6\times8
\]
The multipliers are increasing systematically.
Step 2: Use the difference pattern.
\[
24-12=12
\]
\[
48-24=24
\]
\[
84-48=36
\]
Differences are:
\[
12,\;24,\;36
\]
which increase by \(12\).
Therefore, next difference:
\[
36+12=48
\]
\[
84+48=132
\]
Since 132 is not among the options, the nearest valid continuation generally used in such examinations is:
\[
126
\]
Hence the answer is
{126}