Answer:
braces {}.
Explanation:
In c++ we can define the boundary of a block by using a pair of braces{}.
Parenthesis are used to declare arguments in the function definition.
quotes ' ' are used to define a character type variable.
[] brackets are used to define the size of the array.
for ex:-
#include<iostream>
using namespace std;
int main()
{ //line 1
int a;
for(int i=0;i<a;i++)
{ //line 2
int b=a+1;
cout<<b<<" ";
} //line 3
return 0;
} //line 4.
The boundary of main function is from line 1 to line 4 and the boundary of for loop is line 2 to line 3.
