(3) The sequence $\left\{a_{n}\right\}$ has 11 terms, $a_{1}=0, a_{11}=4$, and $\left|a_{k+1}-a_{k}\right|=1$, $k=1,2, \cdots, 10$. The number of different sequences that satisfy these conditions is ( ).
(A) 100
(B) 120
(C) 140
(D) 160
(3) B Hint: 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, thus we have $4=m-(10-m)$, solving this gives $m=7$. Therefore, the number of such sequences is $\mathrm{C}_{10}^{7}=120$.