#include<bits/stdc++.h>
using namespace std;

#define int long long
const int N=3e5+100,INF=1e18;
#define gc getchar()
#define rd read()
inline int read(){
	int x=0,f=0; char c=gc;
	for(;c<'0'||c>'9';c=gc) f|=(c=='-');
	for(;c>='0'&&c<='9';c=gc) x=(x<<1)+(x<<3)+(c^48);
	return f?-x:x;
}

int n,k,ans,a[N],pre[N],nxt[N];

void solve(){
	
	n=rd,k=rd,ans=1; for(int i=1;i<=n;++i) a[i]=rd;
	pre[0]=0; for(int i=1;i<=n;++i) pre[i]=__gcd(pre[i-1],a[i]);
	nxt[n+1]=0; for(int i=n;i;--i) nxt[i]=__gcd(nxt[i+1],a[i]);
	
	for(int l=1;l<=n;++l)
	//	if(pre[l-1]!=pre[l])
			for(int r=l,lst=0;r<=n;++r)
				lst=__gcd(lst,a[r]+k),ans=max(ans,__gcd(pre[l-1],__gcd(lst,nxt[r+1])));
	
	printf("%lld\n", ans);
	
}

signed main(){
	
	int T=rd;
	while(T--) solve(); 
	
	return 0;
}