#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;
using u32 = unsigned;

template<typename T>
struct RMQ {
    int n;
    std::vector<int> BIT;
    std::vector<std::vector<T>> st;

    RMQ() {}
    RMQ(const std::vector<T> &v) {
        init(v);
    }

    void initBIT(int n) {
        BIT.resize(n + 1);
        for(int i = 2; i <= n; i ++ ) {
            BIT[i] = BIT[i / 2] + 1;
        }
    }

    void init(const std::vector<T> &v) {
        n = v.size();

        initBIT(n);

        const int K = BIT[n];
        st.assign(n, std::vector<T>(K + 1));

        for(int i = 0; i < n; i ++ ) {
            st[i][0] = v[i];
        }
        for(int x = 1; x <= K; x ++ ) {
            for(int i = 0; i + (1 << x) - 1 < n; i ++ ) {
                st[i][x] = std::gcd(st[i][x - 1], st[i + (1 << (x - 1))][x - 1]);
            }
        }
    }

    T query(int l, int r) {
        if(l == r) return 0;
        int B = BIT[r - l + 1];
        return std::gcd(st[l][B], st[r - (1 << B) + 1][B]);
    }

};

void solve() {
    i64 n, k;
    std::cin >> n >> k;

    std::vector<i64> g(n + 2), rg(n + 2), a(n + 2);
    for(int i = 1; i <= n; i ++ ) {
        std::cin >> a[i];
        g[i] = std::gcd(g[i - 1], a[i]);
    }

    for(int i = n; i >= 1; i -- ) {
        rg[i] = std::gcd(rg[i + 1], a[i]);
    }
    for(int i = 1; i <= n; i ++ ) {
        a[i] += k;
    }

    RMQ<i64> rmq(a);
    i64 ans = g[n];

    for(int i = 1; i <= n; i ++ ) {
        int j = i + 1;
        while(j < n and g[j] == g[i]) j ++;
        if(j == n) break;
        for(int r = n; r > j; r -- ) {
            int l = r - 1;
            while(l > j and std::gcd(rg[l], g[i]) == std::gcd(rg[r], g[i])) l --;
            ans = std::max(ans, std::gcd(std::gcd(g[i], rg[r]), rmq.query(j, l)));
            r = l + 1;
        }
        i = j - 1;
    }
    
    for(int i = 1; i <= n; i ++ ) {
        ans = std::max(ans, std::gcd(g[i - 1], rmq.query(i, n)));
    }

    for(int i = n; i >= 1; i -- ) {
        ans = std::max(ans, std::gcd(rg[i + 1], rmq.query(1, i)));
    }

    std::cout << ans << '\n';
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int t = 1;
    std::cin >> t;
    
    while (t--) {
        solve();
    }
    
    return 0;
}