给定一个无向图，图的节点编号从 0 到 n-1，图的边以邻接表的形式给出。下面的程序使用深度优先搜索（DFS）遍历该图，并输出遍历的节点顺序。横线处应该填入的是（ ）

#include <iostream>
#include <vector>
#include <stack>
using namespace std;

void DFS(int start, vector<vector<int>>& graph, vector<bool>& visited) {
    stack<int> s;
    s.push(start);
    visited[start] = true;

    while (!s.empty()) {
        int node = s.top();
        s.pop();
        cout << node << " "; // 输出当前节点

        // 遍历邻接节点
        for (int neighbor : graph[node]) {
            if (!visited[neighbor]) {
                __________________
                __________________
            }
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;

    vector<vector<int>> graph(n);
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    vector<bool> visited(n, false);

    // 从节点 0 开始DFS遍历
    DFS(0, graph, visited);

    return 0;
}

A.

visited[neighbor] = true;
s.push(neighbor-1);

B.

visited[neighbor] = true;
s.push(neighbor+1);

C.

visited[neighbor] = false;
s.push(neighbor);

D.

visited[neighbor] = true;
s.push(neighbor);

{{ select(1) }}

• A
• B
• C
• D