#include <cstdio>
#include <iostream>

using namespace std;

const int N = 2e5 + 500;

string s, old_s, s_max, s_min, ans;
int n, k, dp_max[N], dp_min[N];


void precompute(){
   s_max = s; s_min = s;
   dp_max[n - 1] = 0; dp_min[n - 1] = 0;
   for(int i = n - 2;i >= 0;i--) {
        if(s[i] == '?') {
            s_max[i] = '0' + ('1' - s_max[i + 1]);
            s_min[i] = s_min[i + 1];
        }
        dp_max[i] = dp_max[i + 1] + (s_max[i] != s_max[i + 1]);
        dp_min[i] = dp_min[i + 1] + (s_min[i] != s_min[i + 1]);
    }
}

bool try_greedy(){
    precompute();
    if(dp_max[0] < k || dp_min[0] > k) return false;
    ans = s;
    int kk = k;
    for(int i = 1;i + 1 < n;i++) {
        if(s[i] != '?') { kk -= ans[i] != ans[i - 1]; continue; }
        if((ans[i - 1] != '0') + (s_max[i + 1] != '0') + dp_max[i + 1] >= kk &&
            (ans[i - 1] != '0') + (s_min[i + 1] != '0') + dp_min[i + 1] <= kk) {
            ans[i] = '0';
        } else {
            ans[i] = '1';
        }
        kk -= ans[i] != ans[i - 1];
    }
    return true;
}

void solve(){
    cin >> n >> k;
    cin >> old_s;
    s = old_s;
    if((s[0] != '1') && s[n - 1] != '1' && k % 2 == 0) {
        s[0] = '0'; s[n - 1] = '0';
        if(try_greedy()) {
            cout << ans << '\n';
            return;
        }
        s = old_s;
    }

    if((s[0] != '1') && s[n - 1] != '0' && k % 2 == 1) {
        s[0] = '0'; s[n - 1] = '1';
        if(try_greedy()) {
            cout << ans << '\n';
            return;
        }
        s = old_s;
    }

    if((s[0] != '0') && s[n - 1] != '1' && k % 2 == 1) {
        s[0] = '1'; s[n - 1] = '0';
        if(try_greedy()) {
            cout << ans << '\n';
            return;
        }
        s = old_s;
    }

    if((s[0] != '0') && s[n - 1] != '0' && k % 2 == 0) {
        s[0] = '1'; s[n - 1] = '1';
        if(try_greedy()) {
            cout << ans << '\n';
            return;
        }
        s = old_s;
    }

    cout << "Impossible\n";
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int T; cin >> T;
    for(;T--;) solve();
}