#include <bits/stdc++.h>

#define f first
#define s second
#define pb push_back
#define mp make_pair

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;

const int N = 300500, inf = 1e9, mod = 998244353;
const ll INF = 1e18;

int sum(int a, int b) {
    a += b;
    if (a >= mod)
        a -= mod;
    return a;
}

int sub(int a, int b) {
    a -= b;
    if (a < 0)
        a += mod;
    return a;
}

int mult(int a, int b) {
    return 1ll * a * b % mod;
}

int bp(int a, int b) {
    int res = 1;
    while (b) {
        if (b & 1)
            res = mult(res, a);
        a = mult(a, a);
        b >>= 1;
    }
    return res;
}

int inv(int x) {
    return bp(x, mod - 2);
}



void solve() {
    ll n, k;
    cin >> n >> k;
    string s3;
    cin >> s3;
    ll K = k;
    for (int b=0;b<2;b++)
    {
        k = K;
        string s = s3;
        if (s[0]=='?') s[0] = '0'+b;
        if (s[0]!='0'+b) continue;
        int y = (b+k)%2;
        if (s[n-1]=='?') s[n-1] = '0'+y;
        if (s[n-1]!='0'+y) continue;
        vector<vector<int>> mx(n+1,vector<int>(2)), mn(n+1,vector<int>(2));
        for (int i=n-1;i>=0;i--)
        {
            if (i==n-1)
            {
                mn[i][0] = mn[i][1] = 0;
                mx[i][0] = mx[i][1] = 0;
                if (s[i]!='?') mx[i]['1'-s[i]] = -mod, mn[i]['1'-s[i]] = mod;
                continue;
            }
            mx[i][0] = max(mx[i+1][1]+1,mx[i+1][0]);
            mx[i][1] = max(mx[i+1][0]+1,mx[i+1][1]);
            mn[i][0] = min(mn[i+1][1]+1,mn[i+1][0]);
            mn[i][1] = min(mn[i+1][0]+1,mn[i+1][1]);
            if (s[i]!='?') mx[i]['1'-s[i]] = -mod, mn[i]['1'-s[i]] = mod;
        }
        int prv = -1;
        if (k>=mn[0][0] and k<=mx[0][0]) prv = 0;
        else
        {
            if (k>=mn[0][1] and k<=mx[0][1]) prv = 1;
            else
            {
                continue;
            }
        }
        string A;
        A += '0'+prv;
        for (int i=1;i<n;i++)
        {
            for (int b=0;b<2;b++)
            {
                int D = 0;
                if (b!=prv) D = 1;
                if (k>=mn[i][b]+D and k<=mx[i][b]+D)
                {
                    k -= D;
                    prv = b;
                    A += '0'+b;
                    break;
                }
            }
        }
        cout << A << "\n";
        return;
    }
    cout << "Impossible\n";
}

int main() {
#ifdef DEBUG
    freopen("input.txt", "r", stdin);
#endif
    ios_base::sync_with_stdio(false);
    int t = 1;
    cin >> t;
    for (int i = 1; i <= t; i++) {
//        cout << "Case #" << i << endl;
        solve();
    }
}