/*
lengli_QAQ
Hope there are no bugs!!!
*/
#include <bits/stdc++.h>
#define fastio std::ios::sync_with_stdio(0); std::cin.tie(0); std::cout.tie(0)
#define all(x) x.begin(),x.end()
#define pb push_back
#define i64 long long

void solve(){
    i64 n,k;
    std::cin>>n>>k;
    std::vector<i64> a(n+2),pre(n+2,0),suf(n+2,0); 
    for(int i=1;i<=n;i++) std::cin>>a[i];
    for(int i=1;i<=n;i++) pre[i]=std::gcd(pre[i-1],a[i]);
    for(int i=n;i>=1;i--) suf[i]=std::gcd(suf[i+1],a[i]);

    i64 res=pre[n];
    i64 la=0;

    for(int i=1;i<=n;i++){
        if(pre[i]==pre[i-1]) continue;
        i64 d=a[i]+k;
        for(int j=i;j<=n;j++){
            d=std::gcd(d,a[j]+k);
            i64 ans=std::gcd(pre[i-1],d);
            ans=std::gcd(suf[j+1],d);
            res=std::max(res,ans);
        }
    }

    std::cout<<res<<"\n";
}

signed main(){
    fastio;
    
    int T;
    std::cin>>T;
    while(T--) solve();
    
    return 0;
}