#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#define int long long
using ll = long long;
using i64 = long long;
const int mod = 998244353;
// #define DEBUG

// 线段树合并信息

void solve() {
    int n,k;std::cin>>n>>k;
    std::vector<int> a(n + 1);
    for(int i = 1;i <= n;i++) std::cin>>a[i];
    std::vector<int> b(n + 1);
    for(int i = 1;i <= n;i++) b[i] = a[i] + k;
    std::vector<int> pre(n + 1),suf(n + 2);
    for(int i = 1;i <= n;i++) pre[i] = std::__gcd(pre[i - 1],a[i]);
    for(int i = n;i >= 1;i--) suf[i] = std::__gcd(suf[i + 1],a[i]);
    int last = 1;
    int nowg = 0;
    int ans = 0;
    for(int i = 1;i <= n;i++) ans = std::__gcd(ans, a[i]);
    for(int i = 1;i <= n;i++){
        int glr = std::__gcd(pre[last],suf[i]);
        int glR = std::__gcd(pre[last], suf[i + 1]);
        int gLr = std::__gcd(pre[last - 1], suf[i]);
        int g1 = std::gcd(nowg, b[i]),g2 = std::gcd(nowg, b[last]);
        ans = std::max({ans, std::__gcd(glr, nowg), std::__gcd(glR, g1), std::__gcd(gLr, g2)});
        if(std::__gcd(b[last], b[i]) == 1) last = i,nowg = 0;
    }
    std::cout<<ans<<'\n';
}

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    int t = 1;
    // int res = 0;
    // for(int i = 1;i <= 1145;i++) res |= i;
    // std::cerr<<res<<'\n';
    std::cin>>t;
    while (t--) {
        solve();
    }
    return 0;
}