#include<bits/stdc++.h>
#define ll long long
#define pii make_pair
#define pb push_back
#define rep(i,a,b) for(int i=a;i<=b;++i)
#define per(i,b,a) for(int i=b;i>=a;--i)
const ll inf = 1145141919810;
using namespace std;
inline ll read() {
	ll x=0,f=1;
	char c=getchar();
	while (c<'0' || c>'9') {
		if (c=='-')  f=-1;
		c=getchar();
	}
	while (c>='0' && c<='9') {
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
inline void print(ll x) {
	if(x < 0) putchar('-'), x = -x;
	if(x > 9) print(x / 10);
	putchar(x % 10 + '0');
	return ;
}
inline void pprint(ll x) {
	print(x);
	puts("");
}
int n, m;
vector<vector<pair<int,int> > > g;
const int N = 1e5 + 7;
int fa[N];
ll dis[N];
int get(int x) {
	return fa[x] == x ? x : fa[x] = get(fa[x]);
}

const int M = 1e5 + 7;
int nxt[M << 1], to[M << 1], head[N], w[M << 1], cnt = 1;
void add(int x, int y, ll z){
	nxt[++cnt] = head[x];
	to[cnt] = y;
	w[cnt] = z;
	head[x] = cnt;
}
void slv() {
	n = read(), m = read(); cnt = 1;
	rep(i, 0, n) fa[i] = i, head[i] = 0;
	vector<int> ans;
	int f = 0;
	int st = 0, ed = 0;
	rep(i, 1, m) {
		int x = read(), y = read();
		if(f) continue;
		int fx = get(x), fy = get(y);
		if(fx == fy) {
			st = x, ed = y;
			f = 1;
			ans.pb(i);
			continue;
		}
		fa[fx] = fy;
		add(x, y, i);
		add(y, x, i);
	}

	if(!f) {
		puts("-1");
		return ;
	}

	vector<int> pre(n + 1);
	queue<int> q;

	q.push(st);
	while(q.size()){
		int x = q.front();
		q.pop();
		for(int i = head[x]; i; i = nxt[i]){
			if(!pre[to[i]] && to[i] != st){
				q.push(to[i]);
				pre[to[i]] = (i ^ 1);
			}
		}
	}

	for(int i = ed; i != st; i = to[pre[i]]){
		ans.pb(w[pre[i]]);
	}
	sort(ans.begin(), ans.end());
	rep(i, 0, (int)ans.size() - 1){
		printf("%d%c", ans[i], i == (int)ans.size() - 1 ? '\n' : ' ');
	}
}
int main() {
	int T = read();
	while(T--) {
		slv();
	}
	return 0;
}