// MagicDark
#include <bits/stdc++.h>
#define int long long
#define debug cerr << "\33[32m[" << __LINE__ << "]\33[m "
#define SZ(x) ((int) x.size() - 1)
#define all(x) x.begin(), x.end()
#define ms(x, y) memset(x, y, sizeof x)
#define F(i, x, y) for (int i = (x); i <= (y); i++)
#define DF(i, x, y) for (int i = (x); i >= (y); i--)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
template <typename T> T& chkmax(T &x, T y) {return x = max(x, y);}
template <typename T> T& chkmin(T &x, T y) {return x = min(x, y);}
template <typename T> T& read(T &x) {
	x = 0; int f = 1; char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') f = - f;
	for (; isdigit(c); c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
	return x *= f;
}
const int N = 1e6 + 10;
int n, a[N];
vector <pair <int, int>> ans;
void zhk() {
	ans.clear();
	read(n);
	vector <int> g[2];
	F(i, 1, n) read(a[i]), g[a[i] & 1].push_back(a[i]);
	F(i, 0, 1) sort(all(g[i]));
	if (g[0].empty() || g[1].empty()) {
		vector <int> w[2];
		auto ins = [&] (int x) {
			w[(x >> 1) & 1].push_back(x);
		};
		F(i, 1, n) ins(a[i]);
		while (w[0].size() >= 2 || w[1].size() >= 2) {
			if (w[0].size() >= 2) {
				int x = w[0][SZ(w[0]) - 1], y = w[0][SZ(w[0])];
				ans.emplace_back(x, y);
				ins((x + y) / 2);
				w[0].pop_back();
				w[0].pop_back();
			}
			if (w[1].size() >= 2) {
				int x = w[1][SZ(w[1]) - 1], y = w[1][SZ(w[1])];
				ans.emplace_back(x, y);
				ins((x + y) / 2);
				w[1].pop_back();
				w[1].pop_back();
			}
		}
		if (w[0].size() && w[1].size()) ans.emplace_back(w[0][0], w[1][0]);
	} else {
		// F(i, )
	}
	assert(ans.size() == n - 1);
	// cout << ans.size() << '\n';
	for (auto [i, j]: ans) {
		assert((i + j) % 2 == 0);
		cout << i << ' ' << j << '\n';
	}
}
signed main() {
	int _ = 1;
	cin >> _;
	while (_--) zhk();
	return 0;
}
/* why?
*/