#include<stdio.h>
#include<algorithm>
#include<vector>
#define N 100010
using namespace std;
vector<pair<int,int> >ed[N];
int f[N],rank[N];
int t,n,m;
pair<int,int>b[N];
int anss,ansy;
int stac[N],lens;
int flag;
int find(int x){return f[x]==x?x:(f[x]=find(f[x]));}
int merge(int x,int y){
    int fx=find(x),fy=find(y);
    if(rank[fx]<rank[fy])f[fx]=fy;
    else f[fy]=fx;
    if(rank[fx]==rank[fy])rank[fx]++;
    return 0;
}
int dfs(int x,int fa){
    if(x==ansy){
        flag=1;
        return 0;
    }
    for(vector<pair<int,int> >::iterator it=ed[x].begin();it!=ed[x].end();it++)if(it->first!=fa&&it->second<=anss){
        stac[++lens]=it->second;
        dfs(it->first,x);
        if(flag)return 0;
        lens--;
    }
    return 0;
}



int main(){
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&m);
        for(int i=1;i<=m;i++){
            int x,y;
            scanf("%d%d",&x,&y);
            ed[x].push_back(make_pair(y,i));
            ed[y].push_back(make_pair(x,i));
            b[i]=make_pair(x,y);
        }
        for(int i=1;i<=n;i++)f[i]=i,rank[i]=1;
        lens=0;flag=0;
        for(int i=1;i<=m;i++){
            if(find(b[i].first)==find(b[i].second)){
                anss=i;
                ansy=b[i].second;
                dfs(b[i].first,0);
                stac[++lens]=i;
                break;
            }else merge(b[i].first,b[i].second);
        }
        sort(stac+1,stac+lens+1);
        if(flag)for(int i=1;i<=lens;i++)printf("%d%c",stac[i]," \n"[i==lens]);
        else puts("-1");

        for(int i=1;i<=n;i++)ed[i].clear();
    }
    return 0;
}