#include<bits/stdc++.h>
using namespace std;
#define int long long 
const int nn=3e5+5;
inline int read(){
	int k=0;
	char c=getchar();
	while(c<'0'||c>'9') c=getchar();
	while(c>='0'&&c<='9') k=(k<<3)+(k<<1)+(c^48),c=getchar();
	return k;
}
int a[nn],pre[nn],suf[nn],n,k,ans;
inline int gcd(int a,int b){
	if(b==0) return a;
	return gcd(b,a%b);
}
inline void work(){
	n=read(),k=read();
	for(int i=1;i<=n;i++) a[i]=read();
	for(int i=1;i<=n;i++) pre[i]=gcd(a[i],pre[i-1]);
	suf[n+1]=0;
	for(int i=n;i>=1;i--) suf[i]=gcd(a[i],suf[i+1]);
	ans=pre[n];
	for(int i=1;i<=n;i++){
		if(pre[i]!=pre[i-1]){
			int d=0;
			for(int j=i;j<=n;j++){
				d=gcd(d,a[j]+k);
				ans=max(ans,gcd(d,gcd(pre[i-1],suf[j+1])));
			}
		}
	}
	cout<<ans<<endl;
}
signed main(){
	int t;
	cin>>t;
	while(t--) work();
	return 0;
}