#include <bits/stdc++.h>
#define all(x) (x).begin(),(x).end()

using namespace std;
using ll = long long;

ll Get(vector<ll>& a, int l, int r) {
    if (r < 0) return 0;
    if (l > r) return 0;
    return a[r] - (l ? a[l - 1] : 0);
}

int WhoWin(ll first, ll second, vector<ll>& sa, vector<ll>& sb, int i, int n, ll k) {
    if (first < k && second >= k) return 1;
    if (first >= k) return 2;
    int left = i;
    int right = n - 1;
    int mid;
    int res = n;
    while (left <= right) {
        mid = (left + right) / 2;
        if (first + Get(sa, i, mid) >= k || second + Get(sb, i, mid) >= k) {
            right = mid - 1;
            res = mid;
        } else {
            left = mid + 1;
        }
    }
    if (res == n) {
        return 3;
    }
    if (first + Get(sa, i, res) >= k && second + Get(sb, i, res) >= k) {
        return 3;
    }
    if (first + Get(sa, i, res) >= k) return 2;
    return 1;
}

void Solve() {
    int n, k;
    cin >> n >> k;
    vector<ll> a(n), b(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < n; i++) cin >> b[i];
    vector<ll> sa, sb;
    sa = a;
    sb = b;
    for (int i = 1; i < n; i++) {
        sa[i] += sa[i - 1];
        sb[i] += sb[i - 1];
    }
    if (WhoWin(0, 0, sa, sb, 0, n, k) == 1) {
        cout << 0 << "\n";
        cout << "\n";
        return;
    }
    vector<int> ans;
    ll first = 0;
    ll second = 0;
    for (int i = 0; i + 1 < n; i++) {
        first += a[i];
        second += b[i];
        if (first >= k) {
            cout << "-1\n";
            return;
        }
        if (second >= k) {
            cout << ans.size() << "\n";
            for (int i : ans) {
                cout << i + 1 << " ";
            }
            cout << "\n";
            return;
        }
        if (first + a[i + 1] >= k) {
            ans.push_back(i);
            ll dlt = min(first, second);
            first -= dlt;
            second -= dlt;
        }
        ll prefirst = first;
        ll presecond = second;
        ll dlt = min(first, second);
        if (dlt > 0) {
            prefirst = first - dlt;
            presecond = second - dlt;
            if (WhoWin(prefirst, presecond, sa, sb, i + 1, n, k) == 1) {
                ans.push_back(i);
                cout << ans.size() << "\n";
                for (int i : ans) cout << i + 1 << " ";
                cout << "\n";
                return;
            }
        }
        if (WhoWin(first, second, sa, sb, i + 1, n, k) == 1) {
            cout << ans.size() << "\n";
            for (int i : ans) {
                cout << i + 1 << " ";
            }
            cout << "\n";
            return;
        }
    }
    cout << "-1\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int t;
    cin >> t;
    while (t--) {
        Solve();
    }
}