#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<unordered_map>
#include<vector>
#include<bitset>
#include<queue>
#include<set>
#include<map>
using namespace std;
#define int long long
#define lc (x<<1)
#define rc (x<<1|1)
#define pii pair<int,int>
#define mkp make_pair
#define fi first
#define se second
#define min(x,y) (x>y?y:x)
#define max(x,y) (x<y?y:x)
const int Mx=500005,p=998244353;
int read(){
	char ch=getchar();
	int Alice=0,Aya=1;
	while(ch<'0'||ch>'9'){
		if(ch=='-') Aya=-Aya;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9')
		Alice=(Alice<<3)+(Alice<<1)+(ch^48),ch=getchar();
	return (Aya==1?Alice:-Alice);
}
int n,k;
string s;
int Calc(string t){
	char lst=t[0];
	int res=0;
	for(char c:t){
		if(c!=lst) res++;
		lst=c;
	}
	return res;
}
priority_queue<string,vector<string>,greater<string> >q;
void Solve(string t){
	string r=t;
	for(char &c:r){
		if(c=='?') c='0';
	}
	int ans=Calc(r);
	//cout<<r<<" "<<ans<<endl;
	int cnt=k-ans;
	if(cnt%2!=0) return;
	cnt/=2;
	if(cnt<0){
		cnt=-cnt;
		for(int i=n-2;i>=1;i--){
			if(cnt&&'0'==r[i-1]&&'1'==r[i+1]&&t[i]=='?'){
				r[i]='1';
			}
			if(cnt&&r[i]!=r[i-1]&&r[i]!=r[i+1]&&t[i]=='?'){
				r[i]='1';
				cnt--;
			}
		}
	}
	else if(cnt>0){
		for(int i=n-2;i>=1;i--){
			if(cnt&&r[i]==r[i-1]&&r[i]==r[i+1]&&t[i]=='?'){
				r[i]='1';
				cnt--;
			}
			
		}
	}
	
	if(cnt==0){
		for(int i=1;i+1<n;i++){
			if(r[i]=='1'&&r[i-1]!=r[i+1]&&t[i]=='?'){
				r[i]='0';
			}
		}
		q.push(r);
	}
}
signed main(){
	int T=read();
	while(T--){
		n=read(),k=read();
		cin>>s;
		if(s[0]=='?'){
			string t=s;
			for(char c='0';c<='1';c++){
				t[0]=c;
				if(t[n-1]=='?'){
					for(char d='0';d<='1';d++){
						t[n-1]=d;
						
						Solve(t);t[n-1]='?';
					}
				}
				else{
					Solve(t);
				}
			}
		}
		else if(s[0]!='?'&&s[n-1]=='?'){
			string t=s;
			for(char c='0';c<='1';c++){
				t[n-1]=c;
				Solve(t);t[n-1]='?';
			}
		}
		else Solve(s);
		if(!q.empty()){
			cout<<q.top()<<endl;
		}
		else{
			cout<<"Impossible"<<endl;
		}
		while(!q.empty()) q.pop();
	}
	return 0;
}
/*
Hello!!
Sample:

-------------------
*/