#include<bits/stdc++.h>
const int P = 998244353;
typedef long long ll;
#define rep(i,x,y) for (int i=(x);i<=(y);++i)
using namespace std;
void solve() {
	int n, k;
	cin >> n >> k;
	vector<int>a(n + 1);
	vector<int>last(n + 2);
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	int en = 0;
	for (int i = n; i >= 1; i--) {
		last[i] = __gcd(a[i], en);
		en = last[i];
	}
	int g = 0;
	int ans = 0;
	for (int i = 1; i <= n; i++) {
		if (g != __gcd(g, a[i])) {
			int cntg = 0;
			for (int j = i; j <= n; j++) {
				cntg = __gcd(cntg, a[j] + k);
				ans = max(ans, __gcd(__gcd(cntg, g), last[j + 1]));
			}
		}
		g=__gcd(g,a[i]);
	}
	cout << ans << endl;
	return;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int t = 1;
	cin >> t;
	while (t--) solve();
	return 0;
}
/*
2
6 2
5 3 13 8 10 555
3 0
3 6 9
*/