#include <bits/stdc++.h>

using namespace std;

#define int long long

using vi = vector<int>;
using pii = pair<int, int>;

struct dsu {
    vi fa;

    dsu(int n = 0) : fa(n + 1, -1) {};

    int getfa(int x) {
        if (fa[x] < 0) return x;
        return fa[x] = getfa(fa[x]);
    }

    bool same(int x, int y) {
        x = getfa(x), y = getfa(y);
        return x == y;
    }

    void merge(int x, int y) {
        x = getfa(x), y = getfa(y);
        if (x == y) return;
        if (fa[x] > fa[y]) swap(x, y);
        fa[x] += fa[y], fa[y] = x;
        return;
    }
};

void solve() {
    int n, m, root = -1;
    cin >> n >> m;
    vector<pii> e(m);
    for (auto &[x, y]: e) cin >> x >> y;
    dsu d(n);
    vector g(n + 1, vector<pii>());
    for (int i = 0; const auto &[x, y]: e) {
        g[x].emplace_back(y, i), g[y].emplace_back(x, i);
        i++;
        if (d.same(x, y)) {
            root = x;
            break;
        }
        d.merge(x, y);
    }
    if (root == -1) {
        cout << "-1\n";
        return;
    }

    vi vis(m + 1), res;
    auto dfs = [g, &vis, & res](auto &&self, int x, int fa, int t) -> void {
        if (!res.empty()) return;
        if (t == 1) {
            for (auto [y, id]: g[x]) {
                if (y == fa) continue;
                if (vis[id] == 2) {
                    for (int i = 0; i < vis.size(); i++)
                        if (vis[i] == 2) res.push_back(i + 1);
                    return;
                }
                vis[id] = 2;
                self(self, y, x, 1);
                vis[id] = 1;
            }
        } else {
            for (auto [y, id]: g[x]) {
                if (y == fa) continue;
                if (vis[id] == 1) {
                    vis[id] = 2;
                    self(self, y, x, 1);
                    vis[id] = 1;
                } else {
                    vis[id] = 1;
                    self(self, y, x, 0);
                    vis[id] = 0;
                }
            }
        }

        return;
    };
    dfs(dfs, root, -1, 0);
    sort(res.begin(), res.end());
    for (auto i: res)
        cout << i << " \n"[i == res.back()];
    return ;
}


int32_t main() {
    ios::sync_with_stdio(false), cin.tie(nullptr);
    int TC;
    for (cin >> TC; TC; TC--)
        solve();
    return 0;
}