/** gnu specific **/
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
/** contains everything I need in std **/
#include <bits/stdc++.h>

#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(S) ((int)S.size())
#define FOR(i, st_, n) for(int i = st_; i < n; ++i)
#define RFOR(i, n, end_) for(int i = (n)-1; i >= end_; --i)
#define x first
#define y second
#define pb push_back
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef pair<double, double> pdd;
typedef unsigned long long ull;
typedef long double LD;
typedef pair<ull, ull> pull;
using namespace __gnu_pbds;
typedef tree<ll, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
using namespace std;
#ifdef ONPC
mt19937 rnd(228);
#else
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
#endif

// 3 5 10 14 18 20 24
// 0 0 0 0 0 0 0 0 10 10 10 10 0 0 0 0
// g=14, k = 4
int solve()
{
	ll n, k;
	if(!(cin>>n>>k))return 1;
	vector<ll> a(n);
	FOR(i,0,n) cin>>a[i];
	vector<ll> pref(n,0);
	pref[0]=a[0];
	FOR(i,1,n)pref[i]=gcd(pref[i-1],a[i]);
	vector<ll> suf(n+1,0);
	suf[n-1]=a[n-1];
	RFOR(i,n-1,0)suf[i]=gcd(suf[i+1],a[i]);
	//FOR(i,0,n)cout<<pref[i]<<" ";
	//cout<<'\n';
	//FOR(i,0,n)cout<<suf[i]<<" ";
	//cout<<'\n';
	
	set<ll> S;
	ll res=suf[0];
	
	{// on pref
		ll g=0;
		for(int j=0; j<n; ++j)
		{
			g=gcd(g, a[j]+k);
			res=max(res,gcd(g,suf[j+1]));
		}
	}
	FOR(i,0,n)
	{
		if(i==0 || (i==n-1) || (pref[i]!=pref[i-1]) || (pref[i]!=pref[i+1]))
		{
			ll g=0;
			for(int j=i+1; j<n; ++j)
			{
				g=gcd(g, a[j]+k);
				res=max(res,gcd(g,gcd(pref[i],suf[j+1])));
			}
		}
	}
	cout<<res<<'\n';
    return 0;
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int TET = 1e9;
    cin >> TET;
    for (int i = 1; i <= TET; i++)
    {
        if (solve())
        {
            break;
        }
#ifdef ONPC
        cout << "__________________________" << endl;
#endif
    }
#ifdef ONPC
    cerr << endl << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl;
#endif
}