Which bitwise operator is suitable for turning off a particular bit in a number?

Which bitwise operator is suitable for turning off a particular bit in a number?

2) What should be the value of i and k at the end of the following program segments?

 int i,j,k;
 {
  j=5;
  i=2*j/2;
  k=2*(j/2);
 }

3) Consider the following program segment:

 main()
 {
   int a,b,c;
   b=3;
   a=2;
   a=2*(b++);
   c=2*(++b);
 }

4) Consider the following code fragment:

  int a,c; c=2;
 a=(c+ =5)*2

5) Consider the following statements:

 int a=2, b=3, c=4;
 a=(b++) +c;
 b=a+(++c);