#include <algorithm>
#include <cstdio>
#include <vector>
using namespace std;
namespace Patakou {
const int N = 114514;
int f[N];
vector<pair<int, int> > G[N];
int stk[N], top;
inline int read() {
  int x;
  scanf("%d", &x);
  return x;
}
inline void add(int x, int y, int z) {
  G[x].push_back(make_pair(y, z));
  G[y].push_back(make_pair(x, z));
}
int get(int x) { return f[x] == x ? x : f[x] = get(f[x]); }
void dfs(int x, int t, int father) {
  if (x == t) {
    sort(stk + 1, stk + top + 1);
    for (int i = 1; i < top; ++i) printf("%d ", stk[i]);
    printf("%d\n", stk[top]);
    return;
  }
  for (auto y : G[x]) {
    if (y.first == father) continue;
    ++top;
    stk[top] = y.second;
    dfs(y.first, t, x);
    --top;
  }
}
int QAQ() {
  int T = read();
  while (T--) {
    int n = read(), m = read();
    for (int i = 1; i <= n; ++i) f[i] = i, G[i].clear();
    bool flag = true;
    for (int i = 1; i <= m && flag; ++i) {
      int x = read(), y = read();
      if (get(x) == get(y)) {
        flag = false;
        top = 1;
        stk[top] = i;
        dfs(x, y, 0);
        break;
      }
      add(x, y, i);
      f[get(x)]=get(y);
    }
    if (flag) puts("-1");
  }
  return 0;
}
}  // namespace Patakou
int main() { return Patakou::QAQ(); }