#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=(a); i<(b); i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
using namespace std;

typedef pair<int,int> pii;

void solve() {
	int n, m;
	scanf("%d%d", &n, &m);
	vector<vector<pii> > G(n);
	vector<pii> edges;
	rep(i,0,m) {
		int x, y;
		scanf("%d%d", &x, &y);
		x--, y--;
		edges.emplace_back(x, y);
	}

	vector<int> dsu(n, -1);

	function<int(int)> fnd = [&](int x) { return dsu[x]<0 ? x : dsu[x]=fnd(dsu[x]); };
	auto mrg = [&](int x, int y) {
		int fx = fnd(x), fy = fnd(y);
		if(fx == fy) return false;
		if(dsu[fx] < dsu[fy]) swap(fx, fy);
		dsu[fy] += dsu[fx], dsu[fx] = fy;
		return true;
	};

	rep(i,0,m) {
		auto [x,y] = edges[i];
		if(mrg(x, y)) {
			G[x].emplace_back(y,i);
			G[y].emplace_back(x,i);
			continue;
		}
		vector<int> stk;
		vector<pii> fath(n, pii(-1, -1));
		function<void(int,int)> dfs = [&](int u, int fa) {
			for(auto [v, idx]: G[u]) if(fa != v) {
				fath[v] = pii(u, idx);
				dfs(v, u);
			}
		};
		dfs(x, -1);
		vector<int> idx;
		int p = y;
		while(p != x) {
			idx.push_back(fath[p].second);
			p = fath[p].first;
		}
		idx.push_back(i);
		sort(all(idx));
		rep(j,0,sz(idx)) {
			cout << (idx[j]+1) << " \n"[j==sz(idx)-1];
		}
		return;
	}
	puts("-1");
}
int main(){
	int T;
	scanf("%d", &T);
	while(T--) solve();
	return 0;
}