/**
 * @file qoj6683_1.cpp
 * @author n685
 * @brief
 * @date 2023-08-13
 *
 *
 */
#include <bits/stdc++.h>

#ifdef LOCAL
std::ifstream cin;
std::ofstream cout;
using std::cerr;
#else
using std::cin;
using std::cout;
#define cerr                                                                   \
  if (false)                                                                   \
  std::cerr
#endif

std::string ans;
bool g = false;

void slv(int n, int k, std::string s) {
  auto val = [&s](int ind) { return s[ind] - '0'; };
  std::vector<std::array<int, 2>> f(n), gg(n);
  f[n - 1][1 - val(n - 1)] = (int)1e9;
  gg[n - 1][1 - val(n - 1)] = -(int)1e9;
  for (int i = n - 2; i >= 0; --i) {
    if (s[i] == '?') {
      for (int j : {0, 1}) {
        f[i][j] = std::min(f[i + 1][j], f[i + 1][1 - j] + 1);
        gg[i][j] = std::max(gg[i + 1][j], gg[i + 1][1 - j] + 1);
      }
    } else {
      int v = val(i);
      f[i][v] = std::min(f[i + 1][v], f[i + 1][1 - v] + 1);
      gg[i][v] = std::max(gg[i + 1][v], gg[i + 1][1 - v] + 1);
      f[i][1 - v] = (int)1e9;
      gg[i][1 - v] = -(int)1e9;
    }
  }

  if (f[0][val(0)] % 2 != k % 2)
    return;
  else if (f[0][val(0)] > k || gg[0][val(0)] < k)
    return;
  std::string l = s;
  int pre = 0;
  for (int i = 1; i < n - 1; ++i) {
    if (l[i] == '?') {
      for (char c : {'0', '1'}) {
        int a = (c != l[i - 1]);
        if (f[i][c - '0'] + pre + a <= k && k <= gg[i][c - '0'] + pre + a) {
          l[i] = c;
          break;
        }
      }
    }
    if (l[i] == '?')
      return;
    pre += (l[i] != l[i - 1]);
  }
  g = true;
  ans = std::min(ans, l);
}

void solve() {
  g = false;

  int n, k;
  cin >> n >> k;
  ans.assign(n, '1');

  std::string s;
  cin >> s;
  if (n == 1) {
    if (s == "?")
      cout << "0\n";
    else
      cout << s << '\n';
    return;
  }

  if (s[0] == '?') {
    if (s.back() == '?') {
      for (char c : {'0', '1'}) {
        s[0] = c;
        for (char d : {'0', '1'}) {
          s.back() = d;
          slv(n, k, s);
        }
      }
    } else {
      for (char c : {'0', '1'}) {
        s[0] = c;
        slv(n, k, s);
      }
    }
  } else {
    if (s.back() == '?') {
      for (char d : {'0', '1'}) {
        s.back() = d;
        slv(n, k, s);
      }
    } else
      slv(n, k, s);
  }
  if (!g)
    cout << "Impossible\n";
  else
    cout << ans << '\n';
}

int main() {
#ifdef LOCAL
  cin.open("input.txt");
  cout.rdbuf()->pubsetbuf(0, 0);
  cout.open("output.txt");
#else
  cin.tie(nullptr)->sync_with_stdio(false);
#endif

  int t;
  cin >> t;
  while (t--)
    solve();
}