#include <bits/stdc++.h>
using namespace std;
long long n, m, x, y, z, k, sol, sum, ans, l, r, xx, yy, a[1000000], b[1000000];
pair<long long, pair<long long, long long> > pp[1000000];
pair<long long, long long> p[1000000];
map<long long, long long> ma;
string s1, s2, s;
char c;
int main() {
  cin >> m;
  while (m--) {
    cin >> n;
    vector<long long> v1;
    vector<long long> v2;
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < n; i++) {
      if (a[i] % 2 == 0)
        v1.push_back(i + 1);
      else
        v2.push_back(i + 1);
      if (v2.size() == 2) {
        v1.push_back(v2[v2.size() - 1]);
        v2.pop_back();
        v1.push_back(v2[v2.size() - 1]);
        v2.pop_back();
      }
    }
    if (v1.size() == 0) {
      cout << -1 << endl;
      continue;
    }
    cout << v1.size() << endl;
    sort(v1.begin(), v1.end());
    for (int i = 0; i < v1.size(); i++) cout << v1[i] << " ";
    cout << endl;
  }
  return 0;
}
