Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N, M := sc.nextInt(), sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < M; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	group := make([]int, N)
	for i := 0; i < N; i++ {
		group[i] = -1
	}
	var dfs func(cur int)
	dfs = func(cur int) {
		for i := 0; i < len(G[cur]); i++ {
			next := G[cur][i]
			if group[next] == -1 {
				group[next] = group[cur]
				dfs(next)
			}
		}
	}
	num := 0
	for i := 0; i < N; i++ {
		if group[i] == -1 {
			group[i] = num
			dfs(i)
			num++
		}
	}

	Q := sc.nextInt()
	for i := 0; i < Q; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		if group[s] == group[t] {
			fmt.Fprintln(wtr, "yes")
		} else {
			fmt.Fprintln(wtr, "no")
		}
	}
	wtr.Flush()
}

C++: #include <cstring>
#include <iostream>
#include <vector>

int main() {
    int n, m;
    std::cin >> n >> m;

    int link[n];
    std::vector<std::vector<int>> list;
    for (int i = 0; i < n; i++) {
        link[i] = -1;
    }

    int cnt = 0;
    int s, t;
    for (int i = 0; i < m; i++) {
        std::cin >> s >> t;
        if (link[s] == -1 && link[t] == -1) {
            link[s] = link[t] = cnt;
            cnt++;
            list.emplace_back(std::vector<int>({s, t}));
        } else if (link[s] == -1) {
            link[s] = link[t];
            list[link[t]].emplace_back(s);
        } else if (link[t] == -1) {
            link[t] = link[s];
            list[link[s]].emplace_back(t);
        } else if (link[s] < link[t]) {
            list[link[s]].insert(list[link[s]].end(), list[link[t]].begin(), list[link[t]].end());
            for (auto val : list[link[t]]) {
                link[val] = link[s];
            }
        } else if (link[t] < link[s]) {
            list[link[t]].insert(list[link[t]].end(), list[link[s]].begin(), list[link[s]].end());
            for (auto val : list[link[s]]) {
                link[val] = link[t];
            }
        }
    }

    int q;
    std::cin >> q;
    for (int i = 0; i < q; i++) {
        std::cin >> s >> t;
        if (link[s] == link[t] && link[s] != -1) {
            std::cout << "yes" << std::endl;
        } else {
            std::cout << "no" << std::endl;
        }
    }
}

C++: #include <iostream>
using namespace std;

int root(int x,int par[]){
    if (par[x] == x) return x;
    return par[x]=root(par[x],par);
}

int main(void){
    int n,m,q,s,t,i,rs,rt;
    cin>>n>>m;
    int par[100000];
    for(i=0;i<n;i++)par[i]=i;
    
    for(i=0;i<m;i++){
        cin>>s>>t;
        rs=root(s,par),rt=root(t,par);
        if(rs!=rt)par[rs]=rt;
    }

    for(i=0;i<n;i++){
        par[i]=root(i,par);
    }
    
    cin>>q;
    for(i=0;i<q;i++){
        cin>>s>>t;
        if(par[s]==par[t]){
            cout<<"yes"<<endl;
        }
        else{
            cout<<"no"<<endl;
        }
    }
    
    return 0;
}

C++: #include <iostream>
#include <stack>
#include <vector>
using namespace std;
static const int Max = 100000;
static const int Nil = -1;

int n;
vector<int> G[Max];
int color[Max];

void dfs(int r, int c) {
	stack<int> S;
	S.push(r);
	color[r] = c;
	while (!S.empty()) {
		int u = S.top(); S.pop();
		for (int i = 0; i < G[u].size(); i++) {
			int v = G[u][i];
			if (color[v] == Nil) {
				color[v] = c;
				S.push(v);
			}
		}
	}
	return;
}

void assignColor() {
	int id = 1;
	for (int i = 0; i < n; i++) color[i] = Nil;
	for (int u = 0; u < n; u++) {
		if (color[u] == Nil) dfs(u, id++);
	}
	return;
}

int main() {
	int m;
	cin >> n >> m;
	int s, t;
	for (int i = 0; i < m; i++) {
		cin >> s >> t;
		G[s].push_back(t);
		G[t].push_back(s);
	}
	assignColor();
	int q;
	cin >> q;

	for (int i = 0; i < q; i++) {
		cin >> s >> t;
		if (color[s] == color[t]) {
			cout << "yes" << endl;
		}
		else {
			cout << "no" << endl;
		}
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;
static const int MAX = 100000;
static const int NIL = -1;

int n;
vector<int> G[MAX];
int color[MAX];

void dfs(int r, int c) {
	stack<int> S;
	S.push(r);
	color[r] = c;
	int i, u, v;
	while ( !S.empty() ) {
		u = S.top();
		S.pop();
		for ( i = 0; i < G[u].size(); i++ ) {
			v = G[u][i];
			if ( color[v] == NIL ) {
				color[v] = c;
				S.push(v);
			}
		}
	}
}

void assignColor() {
	int id = 1;
	int i, u;
	for ( i = 0; i < n; i++ ) color[i] = NIL;
	for ( u = 0; u < n; u++ ) {
		if ( color[u] == NIL ) dfs(u, id++);
	}
}

int main() {
	int s, t, m, q, i;

	cin >> n >> m;

	for ( i = 0; i < m; i++ ) {
		cin >> s >> t;
		G[s].push_back(t);
		G[t].push_back(s);
	}

	assignColor();

	cin >> q;

	for ( i = 0; i < q; i++ ) {
		cin >> s >> t;
		if ( color[s] == color[t] ) {
			cout << "yes" << endl;
		} else {
			cout << "no" << endl;
		}
	}

	return 0;
}

C++: #include <iostream>
#include <vector>

std::vector<int> v[100010];
int n;
int m;

bool visited[10010];

/**
bool dfs(int from, int to) {

  if(visited[to]) {
    return true;
  }

  visited[from] = true;
  for(int u=0; u<v[from].size(); ++u) {
    if(visited[v[from][u]]) continue;
    else {
      visited[v[from][u]] = true;
      dfs(v[from][u], to);
    }
  }

  return false;
}
**/

void dfs(int from) {
  visited[from] = true;
  for(int u=0; u<v[from].size(); ++u) {
    if(visited[v[from][u]]) continue;
    else {
      dfs(v[from][u]);
    }
  }
}

int main() {
  std::cin >> n >> m;

  for(int i=0; i<m; ++i) {
    int from, to;
    std::cin >> from >> to;
    v[from].push_back(to);
    v[to].push_back(from);
  }

  int q_n;
  std::cin >> q_n;
  bool answers[10010];
  for(int i=0; i<q_n; ++i) {
    int from, to;
    std::cin >> from >> to;
    for(int j=0; j<n; ++j) visited[j] = false;

    dfs(from);
    answers[i] = visited[to];
  }

  for(int i=0; i<q_n; ++i) {
    if(answers[i]) std::cout << "yes" << std::endl;
    else std::cout << "no" << std::endl;
  }

}