#include<bits/stdc++.h>
using namespace std;
const int N=3e5+10;
int T,n;
long long k,a[N],b[N],pre[N],suf[N];
long long gcd(long long x,long long y) {
    if(!x||!y)return x|y;
    return gcd(y,x%y);
}
int main() {
    scanf("%d",&T);
    while(T--) {
        scanf("%d%lld",&n,&k);
        int cnt=0;
        for(int i=1;i<=n;i++)scanf("%lld",&a[i]);
        for(int i=1;i<=n;i++)if(a[i]!=a[i-1])b[++cnt]=a[i];
        for(int i=1;i<=cnt;i++)pre[i]=gcd(b[i],pre[i-1]);
        b[cnt+1]=0;
        for(int i=cnt;i>=1;i--)suf[i]=gcd(b[i],suf[i+1]);
        long long ans=pre[cnt];
        for(int i=1;i<=cnt;i++) {
            long long cur=0;
            for(int j=i;j<=cnt;j++) {
                cur=gcd(b[j]+k,cur);
                ans=max(ans,gcd(gcd(pre[i-1],suf[j+1]),cur));
                //if(i==2)printf("%d %lld\n",j,cur);
                if(cur<=1)break;
            }
        }
        printf("%lld\n",ans);
    }
}