#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<double, int> pdi;

inline int rd() {
    int x = 0;
    bool f = 0;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) f |= (c == '-');
    for (; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);
    return f ? -x : x;
}

#define eb emplace_back
#define all(s) (s).begin(), (s).end()
#define rep(i, a, b) for (int i = (a); i <= (b); ++i)
#define per(i, a, b) for (int i = (a); i >= (b); --i)

#define N 100007

int f[N];

int find(int x) {return x == f[x] ? x : f[x] = find(f[x]);}

vector<int> ans;

vector<pii> e[N];

bool dfs(int u, int fa, int tar) {
    if (u == tar) return true;
    for (auto [v, id] : e[u]) if (v != fa) {
        ans.eb(id);
        if (dfs(v, u, tar)) return true;
        ans.pop_back();
    }
    return false;
}

inline void work() {
    ans.clear();
    int n = rd(), m = rd();
    rep(i, 1, n) f[i] = i, e[i].clear();
    bool fl = false;
    rep(i, 1, m) {
        int u = rd(), v = rd();
        if (fl) continue;
        if (find(u) != find(v)) {
            f[find(u)] = find(v);
            e[u].eb(v, i);
            e[v].eb(u, i);
        } else {
            fl = true;
            ans.eb(i);
            dfs(u, u, v);
            sort(all(ans));
            bool fr = true;
            for (auto x : ans) {
                if (!fr) putchar(' ');
                printf("%d", x); fr = false;
            }
            puts("");
        }
    }
    if (!fl) puts("-1");
}

int main() {
    per(t, rd(), 1) work();
    return 0;
}