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

#define int long long
#define pb push_back
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];
vector<int> cl,cr;

#define lc (id<<1)
#define rc (id<<1|1)
#define mid (l+r>>1)
int sum[N<<2];
inline void psu(int id){ sum[id]=__gcd(sum[lc],sum[rc]); }
void bui(int id,int l,int r){
	if(l==r) return sum[id]=a[l]+k,void();
	bui(lc,l,mid),bui(rc,mid+1,r),psu(id);
}
int ask(int id,int l,int r,int ql,int qr){
	if(ql<=l&&r<=qr) return sum[id]; int res=0;
	if(ql<=mid) res=__gcd(res,ask(lc,l,mid,ql,qr));
	if(qr>=mid+1) res=__gcd(res,ask(rc,mid+1,r,ql,qr));
	return res;
}

void solve(){
	n=rd,k=rd; 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]);
	
	ans=pre[n],bui(1,1,n);
	cl={}; for(int i=1;i<=n;++i) if(pre[i-1]!=pre[i]) cl.pb(i);
	cr={}; for(int i=1;i<=n;++i) if(nxt[i+1]!=nxt[i]) cr.pb(i);
	for(int l:cl) for(int r:cr) if(l<=r) ans=max(ans,__gcd(pre[l-1],__gcd(ask(1,1,n,l,r),nxt[r+1])));
	printf("%lld\n", ans);
}

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