#include <bits/stdc++.h>


#define N 301000
#define ll long long
using namespace std;

struct bala {
    set<ll> v1;
    set<ll> v2;
    void init() {
        v1.clear();
        v2.clear();
    }
    void v1_insert(ll c) {
        v1.insert(c);
    }
    void v2_insert(ll c) {
        v2.insert(c);
    }
}la[2];
ll a[N], n, k, ans, b[N];
void sl() {
    cin>>n>>k; b[n + 1] = 0;
    for(int i = 1;i <= n; i++) cin>>a[i]; 
    for(int i = n;i >= 1; i--) b[i] = __gcd(b[i + 1], a[i]);
    ans = b[1];
    la[1].v1_insert(a[1]);
    la[1].v2_insert(a[1] + k);
    for(int i = 2;i <= n; i++) {
        int e = i % 2, o = (i - 1) % 2;
        
        la[e].init();
        for(auto it : la[o].v1) {
            la[e].v1_insert(__gcd(it, a[i]));
            la[e].v2_insert(__gcd(it, a[i] + k));
        }
        for(auto it : la[o].v2) {
            la[e].v2_insert(__gcd(it, a[i] + k));
            ans = max(ans, __gcd(it, b[i]));
        } 
    }
    for(auto it : la[n % 2].v2) {
        ans = max(ans, it);
    }
    cout<<ans<<endl;
}
int main() {
    int T; cin>>T;
    while (T--) {
        sl();
    }
    
}