#include<bits/stdc++.h>
#define ios ios::sync_with_stdio(0),cin.tie(0),cout.tie(0)
using namespace std;
using ll = int;
using PLL = pair<ll,ll>;
const ll INF=0x3f3f3f3f;
const ll Q = 1e5+9;
const ll MOD = 1e9 + 7;
pair<ll,ll> tu[Q];
ll a[Q];
int root(ll x){return a[x]==x?x:a[x]=root(a[x]);}
vector<pair<ll,ll>> d[Q];
ll now=0;
vector<ll> ans;
bool okor=false;
void dfs(ll x,ll fa){
    if(okor)return;
    for(auto &[i,u]:d[x]){
        if(i==fa) continue;
        if(i==now){
            ans.push_back(u);
            okor=true;
            return;
        }
        ans.push_back(u);
        dfs(i,x);
        if(okor)return;
         ans.pop_back();
    }
}
void solve(){
   ll n,m;cin>>n>>m;
   okor=false;
   ans.clear();
   now=0;
   for (ll i = 0; i <= max(n,m); i++)
   {a[i]=i;d[i].clear();}
    for (ll i = 1; i <= m; i++)
    {
        cin>>tu[i].first>>tu[i].second;
    }
    ll cnt=0;
    bool isok=false;
    for (ll i = 1; i <= m; i++)
    {
        if(root(tu[i].second)==root(tu[i].first)){
            cnt=tu[i].first;
        d[tu[i].second].push_back({tu[i].first,i});
        d[tu[i].first].push_back({tu[i].second,i});
        isok=true;
        break;
        }
        a[root(tu[i].second)]=root(tu[i].first);
        d[tu[i].second].push_back({tu[i].first,i});
        d[tu[i].first].push_back({tu[i].second,i});
    }
    if(isok==false){
        cout<<-1<<"\n";
        return;
    }
    now=cnt;
    dfs(cnt,-1);
    sort(ans.begin(),ans.end());
   for (ll i = 0; i < ans.size()-1; i++)
   {
    cout<<ans[i]<<" ";
   }
   cout<<ans[ans.size()-1]<<"\n";
}
int main(){
    ll _=1;cin>>_;
    while (_--)solve();
    return 0;
}