#include <bits/stdc++.h>
using LL = long long;

const int maxN = 3e5 + 10;
int T, n;
LL k, a[maxN], pre[maxN], suf[maxN], d[maxN];

LL Labs(LL x) {
	return x > 0 ? x : -x;
}
int main() {
	std::ios::sync_with_stdio(false); std::cin.tie(nullptr);
	std::cin >> T;
	while(T--) {
		std::cin >> n >> k;
		for(int i = 1; i <= n; i++) {
			std::cin >> a[i];
		} 

		pre[1] = a[1];
		suf[n] = a[n];
		for(int i = 2; i <= n; i++) {
			pre[i] = std::__gcd(pre[i - 1], a[i]);
		}
		for(int i = n - 1; i >= 1; i--) {
			suf[i] = std::__gcd(suf[i + 1], a[i]);
		}

		LL ans = pre[n];
		for(int i = 1; i <= n; i++) {
			if(pre[i - 1] != pre[i]) {
				LL t = 0;
				for(int j = i; j <= n; j++) {
					t = std::__gcd(t, a[j] + k);
					ans = std::max(ans, std::__gcd(t, std::__gcd(pre[i - 1], suf[j + 1])));
					// std::cerr << i << " " << j << " " << pre[i - 1] << " " << a[j] + k << " " << t << " " << suf[j + 1] << "\n";
				}
			}
		}

		std::cout << ans << "\n";
	}
	return 0;
}