#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int Maxn = 1e5 + 5;
int f[Maxn], g[Maxn], h[Maxn];
void _init(int N = 1e5)
{
    for(int i = 1; i <= 1e5; i++)
    {
        f[i] = i / 2 * 2;
        g[i] = (i + 1) / 2 * 2;
        h[i] = i;
    }
}
void solve()
{
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    int pd = 0;
    vector<int> len(n + 1), num(n + 1);
    for(int i = n - 1; i >= 0; i--)
    {
        if(s[i] == '?')
        {
            len[i] = len[i + 1] + 1;
        }
    }
    int now = 0, low = 0;
    for(int i = n - 1; i >= 0; i--)
    {
        num[i] = num[i + 1];
        if(s[i] == '?' && (i == 0 || len[i] > len[i - 1]))
        {
            if(i == 0 || i + len[i] == n) num[i] += h[len[i]];
            else if(s[i - 1] != s[i + len[i]])
            {
                low++;
                num[i] += f[len[i]];
            }
            else num[i] += g[len[i]];
        }
        if(i != n - 1 && s[i] != '?' && s[i + 1] != '?' && s[i] != s[i + 1])
        {
            low++;
        }
        //cout << i << " " << len[i] << " " << num[i] << "\n";
    }
    //cout << low << " !\n";
    if(num[0] + low < k || low > k) s = "Impossible";
    else
    {
        int ok = 1;
        if(s[n - 1] != '?' && s[0] == '?' && len[0] != n)
        {
            if((k - low) % 2)
            {
                if(s[len[0]] == '0') s[0] = '1';
                else s[0] = '0';
                low++;
            }
            else
            {
                if(s[len[0]] == '0') s[0] = '0';
                else s[0] = '1';
            }
        }
        
        for(int i = 0; i < n; i++)
        {
            if(s[i] == '?')
            {
                int l, r;
                l = low;
                if(i != 0 && s[i - 1] != '0') l++;
                if(i + len[i] != n && s[i + len[i]] != '0') l++;
                if(i != 0 && i + len[i] != n && s[i - 1] != s[i + len[i]]) l--;
                r = l + num[i + 1];
                if(i + len[i] == n)
                {
                    r += h[len[i] - 1];
                }
                else if(s[i + len[i]] != '0')
                {
                    r += f[len[i] - 1];
                }
                else r += g[len[i] - 1];
                //cout << i << " " << s << " " << l << " " << r << " " << low << "\n";
                if(l <= k && k <= r)
                {
                    s[i] = '0';
                    if(i != 0 && s[i - 1] != '0') low++;
                    if(i + len[i] != n && s[i + len[i]] != '0') low++;
                    if(i != 0 && i + len[i] != n && s[i - 1] != s[i + len[i]]) low--;
                    continue;
                }
                l = low;
                if(i != 0 && s[i - 1] != '1') l++;
                if(i + len[i] != n && s[i + len[i]] != '1') l++;
                if(i != 0 && i + len[i] != n && s[i - 1] != s[i + len[i]]) l--;
                r = l + num[i + 1];
                if(i + len[i] == n)
                {
                    r += h[len[i] - 1];
                }
                else if(s[i + len[i]] != '1')
                {
                    r += f[len[i] - 1];
                }
                else r += g[len[i] - 1];
                //cout << i << " " << s << " " << l << " " << r << "\n";
                if(l <= k && k <= r)
                {
                    s[i] = '1';
                    if(i != 0 && s[i - 1] != '1') low++;
                    if(i + len[i] != n && s[i + len[i]] != '1') low++;
                    if(i != 0 && i + len[i] != n && s[i - 1] != s[i + len[i]]) low--;
                    continue;
                }
                ok = 0;
                break;
            }
        }
        if(!ok) s = "Impossible";
    }
    cout << s << "\n";
}
int main()
{
    cin.tie(0)->sync_with_stdio(false);
    _init();
    int T;
    cin >> T;
    while(T--) solve();
    return 0;
}