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

#define int long long

struct DSU {
	vector<int> P, S;
	DSU(int n) {
		P.resize(n+1);
		S.resize(n+1, 1);
		for (int i = 1; i <= n; i++) P[i] = i;
	}
	
	int find(int x) {
		if (x == P[x]) return x;
		return P[x] = find(P[x]);
	}
	
	bool merge(int a, int b) {
		a = find(a); b = find(b);
		if (a == b) return 0;
		if (S[a] < S[b]) swap(a, b);
		
		S[a] += S[b];
		P[b] = a;
		return 1;
	}
	
	int same(int a, int b) {
		return find(a) == find(b);
	}
};

int par[100001], pid[100001], hei[100001];
vector<pair<int, int>> adj[100001];

void dfs(int now, int prv, int h, int pri) {
	hei[now] = h;
	par[now] = prv;
	pid[now] = pri;

	for (auto [u, i]: adj[now]) {
		if (u != prv) {
			dfs(u, now, h+1, i);
		}
	}
}

void solve() {
	int n, m; cin >> n >> m;
	DSU d(n); vector<tuple<int, int, int>> e;
	bool f = 0;
	for (int i = 1; i <= m; i++) {
		int x, y; cin >> x >> y;
		if (f) continue;
		e.emplace_back(x, y, i);
		if (!d.merge(x, y)) f = 1;
	}
	if (!f) {
		cout << "-1\n";
		return;
	}

	auto [p, q, id1] = e.back(); e.pop_back();
	for (int i = 1; i <= n; i++) {
		adj[i].clear(); par[i] = hei[i] = pid[i] = 0;
	}
	for (auto [u, v, i]: e) {
		adj[u].emplace_back(v, i);
		adj[v].emplace_back(u, i);
	}

	for (int i = 1; i <= n; i++) {
		if (par[i] == 0) {
			dfs(i, i, 1, 0);
		}
	}

	vector<int> ans; ans.push_back(id1);
	if (hei[p] < hei[q]) swap(p, q);
	while (hei[p] > hei[q]) {
		ans.push_back(pid[p]);
		p = par[p];
	} 

	while (p != q) {
		ans.push_back(pid[p]);
		p = par[p];
		ans.push_back(pid[q]);
		q = par[q];
	}

	sort(ans.begin(), ans.end());
	for (int i = 0; i < ans.size(); i++) {
		cout << ans[i];
		if (i+1 == ans.size()) {
			cout << "\n";
		} else {
			cout << ' ';
		}
	}
}

signed main() {
	ios::sync_with_stdio(0); cin.tie(0);

	int t; cin >> t;
	while (t--) {
		solve();
	}

	return 0;
}