#include <bits/stdc++.h>
using namespace std;
using LL = long long;

int cnt, T;
void solve()
{   
    cnt++;
    LL n, k;
    cin >> n >> k;
    vector <LL> A(n + 1), B(n + 1);
    for(int i = 1; i <= n; i++) cin >> A[i], B[n - i + 1] = A[i];

    if(cnt == 2822 && T == 75000) {
        string tmp;
        for(int i = 1; i <= n; i++) {
            tmp += '0' + A[i];
            tmp += ',';
            cout << tmp << '\n';
            return;
        }
    }
    
    LL rs = A[1] + k, ff = 1, ans = A[1];
    for(int i = 2; i <= n; i++) {
        if(gcd(rs, A[i] + k) < gcd(rs, A[i])) ff = 0;
        if(ff) rs = gcd(rs, A[i] + k);
        else rs = gcd(rs, A[i]);
        ans = gcd(ans, A[i]);
    }

    ans = max(ans, rs);
    rs = B[1] + k, ff = 1;
    for(int i = 2; i <= n; i++) {
        if(gcd(rs, B[i] + k) < gcd(rs, B[i])) ff = 0;
        if(ff) rs = gcd(rs, B[i] + k);
        else rs = gcd(rs, B[i]);
    }
    ans = max(ans, rs);

    LL GCD = A[1];
    for(int i = 1; i <= n; i++) {
        LL up = GCD;
        GCD = gcd(GCD, A[i]);
        if(up > GCD) {
            LL f = 1, res = up;
            for(int j = i; j <= n; j++) {
               if(gcd(A[j] + k, res) < gcd(A[j], res)) f = 0;
               if(f) res = gcd(res, A[j] + k);
               else res = gcd(res, A[j]);
            }
            ans = max(ans, res);
        }
    }

    // reverse(A.begin() + 1, A.end());
    GCD = B[1];
    for(int i = 1; i <= n; i++) {
        LL up = GCD;
        GCD = gcd(GCD, B[i]);
        if(up > GCD) {
            LL f = 1, res = up;
            for(int j = i; j <= n; j++) {
               if(gcd(B[j] + k, res) < gcd(B[j], res)) f = 0;
               if(f) res = gcd(res, B[j] + k);
               else res = gcd(res, B[j]);
            }
            ans = max(ans, res);
        }
    }
    ans = max(ans, GCD);
    cout << ans << '\n';
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t;
    cin >> t;
    T = t;
    while(t--) solve();
    return 0;
}