C++ :

#include<iostream>
using namespace std;
const int N = 20005;
int father[N];
int f(int x)
{
	while (father[x]!=x) x=father[x];
	return x;
}
int main()
{
	int n,m,x,y,k1,k2;
	cin>>n>>m;
	for (int i=1;i<=n;i++) father[i]=i;
	for (int i=1;i<=m;i++){
		cin>>x>>y;
		k1=f(x);
		k2=f(y);
		if (k1!=k2) father[k2]=k1;
	}
	int q;
	cin>>q;
	for (int i=0;i<q;i++){
		cin>>x>>y;
		if (f(x)==f(y)) cout<<"Yes\n";
		else cout<<"No\n";
	}
	return 0;
}

Pascal :

program qinqi;
const maxn=100000;
var father:array[1..maxn]of integer;
    n,m,p:integer;
procedure init;
  begin
    fillchar(father,sizeof(father),0);
    read(n,m);
  end;
function getfather(v:integer):integer;
  begin
    if father [v]=0 then getfather:=v
    else begin
    father [v]:=getfather(father [v]);
    getfather:=father [v];
    end;
  end;
procedure merge(i,j:integer);
  begin
    i:=getfather(i);
    j:=getfather(j);
    if i<>j then
    father[i]:=j;
  end;
procedure a;
var k,i,j:integer;
  begin
    for k:=1 to m do
      begin
        read(i,j);
        merge(i,j);
      end;
    read(p);
    for k:=1 to p do
      begin
        read(i,j);
        if getfather(i)=getfather(j)then writeln('Yes')
        else writeln('No');
      end;
  end;
begin
init;
a;
end.