3. Let the sequence $\left\{a_{n}\right\}$ have 11 terms,
$$
a_{1}=0, a_{11}=4 \text {, }
$$

and $\left|a_{k+1}-a_{k}\right|=1(k=1,2, \cdots, 10)$. Then the number of different sequences that satisfy the conditions is ( ).
(A) 100
(B) 120
(C) 140
(D) 160
3. B.

According to the problem, we have $a_{k+1}-a_{k}=1$ or $a_{k+1}-a_{k}=-1$. If there are $m$ ones, then there are $10-m$ negative ones. Therefore, $4=m-(10-m) \Rightarrow m=7$.
Thus, the number of sequences we are looking for is $\mathrm{C}_{10}^{7}=120$.