#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;ll cnt2=0;
vector<ll> ans;
bool okor=false ;
map<ll,pair<ll,ll>>mp;
ll cnt=0;
void bfs(ll x){
    queue<ll> q;
    q.push(x);
    while(q.size()){
        x=q.front();q.pop();
        for (auto &&[i,u] : d[x])
        {
            if(i==cnt2){
                ans.push_back(u);
                while(mp[x].first!=cnt){
                    ans.push_back(mp[x].second);
                    x=mp[x].first;
                }
                ans.push_back(mp[x].second);
                return;
            }
            if(mp[x].first==i) continue;
            mp[i]={x,u};
            q.push(i);
        }

        
    }
}
void solve(){
    mp.clear();
   ll n,m;cin>>n>>m;okor=false ;
   ans.clear();now=0;
   for (ll i = 0; i <= n; i++)
   {
    a[i]=i;d[i].clear();
   }
    for (ll i = 1; i <= m; i++)
    {
        cin>>tu[i].first>>tu[i].second;
    }
    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;cnt2=tu[i].second;
            isok=true;ans.push_back(i);
            break;
        }
        a[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;
    bfs(cnt);
    
    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;
}