2. Figure 1 is the "Yang Hui Triangle" from ancient China. According to the numerical pattern, please fill in all the " $O$ " in the eighth row with the appropriate numbers. Then, the sum of the 36 numbers in the first eight rows is ( ).
(A) 257
(B) 256
(C) 255
(D) 254
2. C.

Notice that each number is the sum of the two adjacent numbers in the row above it, so the eighth row should be: $1, 7, 21, 35, 35, 21, 7, 1$.

Also, the sum of the numbers in each row is exactly twice the sum of the numbers in the row above it. Therefore, the sum of the first eight rows, which consist of 36 numbers, is
$$
1+2+4+8+16+32+64+128=255 .
$$