#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int MAXN=3e5+5;
ll gcd(ll x,ll y) {
	if(!x||!y) return x|y;
	return gcd(y,x%y);
}
ll a[MAXN],k,pre[MAXN],suf[MAXN],val[MAXN];
void solve() {
	int n;
	cin>>n>>k;
	for(int i=1;i<=n;++i) cin>>a[i];
	pre[0]=suf[n+1]=val[0]=0;
	for(int i=1;i<=n;++i) pre[i]=gcd(pre[i-1],a[i]),val[i]=gcd(val[i-1],a[i]+k);
	for(int i=n;i>=1;--i) suf[i]=gcd(suf[i+1],a[i]);
	ll ans=pre[n];
	for(int i=1;i<=n;++i) ans=max(ans,gcd(val[i],suf[i+1]));
	for(int l=2;l<=n;++l) {
		val[l-1]=0;
		for(int r=l;r<=n;++r) {
			ll z=gcd(val[r-1],a[r]+k);
			if(z==val[r]) break;
			val[r]=z,ans=max(ans,gcd(z,gcd(pre[l-1],suf[r+1])));
		}
	}
	cout<<ans<<"\n";
}
signed main() {
	ios::sync_with_stdio(false);
	int T; cin>>T;
	while(T--) solve();
	return 0;
}