#include <bits/stdc++.h>
#pragma GCC optimize(3)
#define int long long
#define llu unsigned long long
#define endl "\n"
#define inf 0x3f3f3f3f
#define debug cout << "****************" << endl
using namespace std;

typedef pair<int, int> PII;

const int N = 1e6 + 7;

void solve()
{
    int n, k;
    cin >> n >> k;
    vector<int> a(n + 7);
    vector<int> pre(n + 7);
    vector<int> suf(n + 7);
    int ans = 0;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    for (int i = 1; i <= n; i++) {
        pre[i] = gcd(pre[i - 1], a[i]);
    }
    for (int i = n; i >= 1; i--) {
        suf[i] = gcd(suf[i + 1], a[i]);
    }
    pre[0] = 1e18;
    for (int i = 1; i <= n; i++) {
        if (pre[i] < pre[i - 1]) {
            int gc = 0;
            for (int j = i; j <= n; j++) {
                gc = gcd(gc, a[j] + k);
                ans = max(ans, gcd(gcd(pre[i - 1], gc), suf[j + 1]));
            }
        }
    }
    ans = max(ans, pre[n]);
    cout << ans << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    cin >> T;
    while (T--)
        solve();
    return 0;
}