#include <bits/stdc++.h>
using namespace std;
using LL = long long;

void solve() {
    int n, m;
    cin >> n >> m;    
    vector<int> fa(n);
    iota(fa.begin(), fa.end(), 0);

    auto find = [&](auto &&self, int u) -> int {
        return (fa[u] == u ? u : fa[u] = self(self, fa[u]));
    };

    int T = -1;
    vector<int> path;
    bool flag = false;
    vector<vector<array<int, 2>>> e(n);
    auto dfs = [&](auto &&self, int u, int fa) -> void {
        if (u == T) {
            flag = true;
            return;
        }
        if (flag) {
            return;
        }

        for (auto [v, w] : e[u]) {
            if (v == fa) {
                continue;
            }
            path.push_back(w);
            self(self, v, u);
            if (flag) {
                return;
            }
            path.pop_back();
        }
    };


    for (int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;

        if (path.size()) {
            continue;
        }
        --u, --v;
        e[u].push_back({v, i});
        e[v].push_back({u, i});
        int x = u, y = v;

        int fx = find(find, x), fy = find(find, y);
        if (fx != fy) {
            fa[fx] = fy;
        } else {
            path.push_back(i);
            T = v;
            dfs(dfs, u, -1);
        }
    }
    if (path.size()) {
        sort(path.begin(), path.end());
        for (int i = 0; i < (int)path.size(); ++i) {
            cout << path[i] + 1 << " \n"[i == (int)path.size() - 1];
        }
    } else {
        cout << -1 << '\n';
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}