#include<bits/stdc++.h>
#define int long long
using namespace std;
int Read(){
	int x=0;
	char ch=getchar();bool f=0;
	while(ch<'0'||ch>'9') if(ch=='-')f=1,ch=getchar(); else if(ch==EOF)return 0; else ch=getchar();
	while(ch>='0'&&ch<='9') x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
	return f?-x:x;
}
int fa[100005];
int findf(int x){
	if(fa[x]==x) return x;
	return fa[x]=findf(fa[x]);
}
int h[100005];
int to[100005];
int nxt[100005];
int cnt;
bool flag[100005];
void link(int x,int y){
	nxt[++cnt]=h[x];
	h[x]=cnt;
	to[cnt]=y;
	nxt[++cnt]=h[y];
	h[y]=cnt;
	to[cnt]=x;
	return;
}
bool vis[100005];
int res=0;
int dfs(int x,int f){
	vis[x]=res;
//	cout<<x<<' '<<f<<":"<<endl;
	for(int i=h[x];i;i=nxt[i]){
		if(to[i]==f) continue;
		int p=to[i];
//		cout<<p<<endl;
		if(vis[p]==res){
			flag[i/2]=1;
			return p;
		}if(vis[p]) continue;
		int k=dfs(p,x);
		if(k){
			flag[i/2]=1;
			if(k==x)return 0;
			return k;
		}
	}
//	cout<<x<<' '<<f<<"end"<<endl;
	return 0;
}
signed main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	int T=Read();
	while(T--){
		int n=Read(),m=Read();
		cnt=1;
		for(int i=1;i<=n;i++) fa[i]=i,h[i]=0,vis[i]=0;
		bool fl=0;
		for(int i=1;i<=m;i++){
			int x=Read(),y=Read();
			if(fl)continue;
			int fax=findf(x),fay=findf(y);
			if(fax==fay)
				fl=1;
			fa[fax]=fay;
			link(x,y);
		}
		res=0;
		if(!fl){
			printf("-1\n");
			for(int i=1;i<=cnt;i++){
				nxt[i]=0;
				to[i]=0;
			}
			continue;
		}
		for(int i=1;i<=n;i++){
			if(!vis[i]){
				res++;
				dfs(i,0);
			}
		}
		bool flg=0; 
		for(int i=1;i<=m;i++)
			if(flag[i]){
				if(!flg){
					flg=1;
					printf("%lld",i);
				}
				else printf(" %lld",i);
			}
		printf("\n");
		for(int i=1;i<=cnt;i++){
			nxt[i]=0;
			to[i]=0;
		}
	}
	return 0; 
}