///警钟敲烂*inf: 没有返回值的函数一定要写成 void 类型，否则会出现 Undefined Behaviour 然后 RE！（这时本地AC） 
#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;

const long long MAXN = 1e6 + 10;
const long long MAXM = 1e6 + 10;

inline long long read() {
	long long x = 0, f = 1;
	char ch = getchar();
	while (!isdigit(ch)) {
		if (ch == '-') f = -1;
		ch = getchar();
	}
	while (isdigit(ch)) {
		x = x * 10 + ch - '0';
		ch = getchar();
	}
	return x * f;
} 

struct node {
	long long to, index;
};

long long n, m, G[MAXM][2], fa[MAXN];
vector<node> G2[MAXN];

long long find(long long x) {
	if (x == fa[x]) return x;
	return fa[x] = find(fa[x]);
}

void unite(long long x, long long y) {
	long long X = find(x);
	long long Y = find(y);
	if (X != Y) fa[X] = Y;
}

long long Start, End;
bool used[MAXM], Used[MAXM];

void dfs(long long u) {
	if (u == End) {
		for (long long i = 1; i <= m; i++)
			Used[i] = used[i];
		return;
	}
	for (long long i = 0; i < G2[u].size(); i++) {
		if (!used[G2[u][i].index]) {
			used[G2[u][i].index] = true;
			dfs(G2[u][i].to);
			used[G2[u][i].index] = false;
		}
	}
}

int main() {
	long long t = read();
	for (long long u = 1; u <= t; u++) {
		n = read(); m = read();
		for (long long i = 1; i <= m; i++) {
			G[i][0] = read();
			G[i][1] = read();	
			used[i] = false;
			Used[i] = false;
		}
		for (long long i = 1; i <= n; i++) {
			fa[i] = i;
			G2[i].clear();
		}
		long long Maxx = -1;
		for (long long i = 1; i <= m; i++) {
			if (find(G[i][0]) == find(G[i][1])) {
				Maxx = i;
				break;
			}
			unite(G[i][0], G[i][1]);
			G2[G[i][0]].push_back((node){G[i][1], i});
			G2[G[i][1]].push_back((node){G[i][0], i}); 
		} 
		if (Maxx == -1) printf("-1\n");
		else {
			Start = G[Maxx][0], End = G[Maxx][1];
			dfs(Start);
			for (long long i = 1; i < Maxx; i++) {
				if (Used[i]) 
					printf("%d ", i);
			}
			printf("%d\n", Maxx);
		}
	}
	return 0;
}