#include <bits/stdc++.h>

using namespace std;

const int N=1e5+10;

int p[N];
vector<pair<int,int>> e[N];

int find(int x)
{
    if(p[x]!=x) p[x]=find(p[x]);
    return p[x];
}

stack<int> stk;
vector<int> ans;

int n,m;

int cur;

void dfs(int u,int fa)
{
    if(u==cur)
    {
        while(!stk.empty())
        {
            int t=stk.top();
            ans.push_back(t);
            stk.pop();
        }
        reverse(ans.begin(),ans.end());
        for(auto x : ans) stk.push(x);
    }
    for(auto [v,w] : e[u])
    {
        if(v==fa) continue;
        stk.push(w);
        dfs(v,u);
        stk.pop();
    }
}

void solve()
{
    cin >> n >> m;
    ans.clear();
    for(int i=1;i<=n;i++) p[i]=i,e[i].clear();
    bool flg=0;
    for(int i=1;i<=m;i++)
    {
        int u,v;
        cin >> u >> v;
        int a=find(u),b=find(v);
        if(flg==1) continue;
        if(a!=b)
        {
            p[a]=b;
            e[u].push_back({v,i});
            e[v].push_back({u,i});
        }
        else
        {
            cur=v;
            dfs(u,0);
            ans.push_back(i);
            sort(ans.begin(),ans.end());
            int sz=ans.size();
            for(int i=0;i<sz;i++) cout << ans[i] << " \n"[i==sz-1];
            flg=1;
        }
    }
    if(!flg) cout << "-1\n";
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int T;
    cin >> T;
    while(T--) solve();

    return 0;
}