/*
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

struct ST{
	std::vector<std::vector<i64>> f;
    int n=0,m=0;
    ST(){};
	ST(int nn,std::vector<i64> &a,i64 k){
        n=nn,m=std::__lg(nn)+1;
        f.resize(n+1,std::vector<i64> (m+1));
		for(int len=0;len<m;len++){
			for(int i=1;i+(1<<len)-1<=n;i++){
				if(!len) f[i][len]=a[i]+k;
				else f[i][len]=std::gcd(f[i][len-1],f[i+(1<<len-1)][len-1]);
			}
		}
	}
	i64 query(int l,int r){
		int k=std::__lg(r-l+1);
        return std::gcd(f[l][k],f[r-(1<<k)+1][k]);
	}
};

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];
    std::vector<int> q;
    ST st(n,a,k);

    i64 la=0;

    for(int i=1;i<=n;i++){
        la=std::gcd(pre[i-1],a[i]+k);
        if(la!=pre[i]) q.pb(i);
        for(auto j:q){
            i64 ans=st.query(j,i);
            ans=std::gcd(suf[i+1],ans);
            ans=std::gcd(pre[j-1],ans);
            res=std::max(res,ans);
        }
    }

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

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