ANS:C - he or she has access

No answer description is available. 

ANS:D - _ (underscore)

Variable names in C are made up of letters (upper and lower case) and digits. The underscore character ("_") is also permitted. Names must not begin with a digit. Examples of valid (but not very descriptive) C variable names:
=> foo
=> Bar
=> BAZ
=> foo_bar
=> _foo42
=> _
=> QuUx

ANS:B - No

No, C can accept upto 127 maximum number of arguments in a function.

ANS:A - Yes

Yes, It will return the value 20*20 = 400 Example:

#include <stdio.h>
int f1(int, int); /* Function prototype */
int f2(int); /* Function prototype */

int main()
{
    int a = 2, b = 3, c;
    c = f1(a, b);
    printf("c = %d\n", c);
    return 0;
}

int f1(int a, int b)
{
    return ( f2(20) );
}

int f2(int a)
{
    return (a * a);
}

ANS:A - Yes

When a recursive call is made, the function/process clones itself and then process that funtion. This leads to time and space constrains. In a loop, there is no recursive call involved that saves a lot of time and space too.

ANS:A - Yes

Yes, too many recursive calls may result into stack overflow. because when a function is called its return address is stored in stack. After sometime the stack memory will be filled completely. Hence stack overflow error will occur.

ANS:B - No

No, In a function two return statements can occur but not successively. Example:

#include <stdio.h>
int mul(int, int); /* Function prototype */

int main()
{
    int a = 0, b = 3, c;
    c = mul(a, b);
    printf("c = %d\n", c);
    return 0;
}

/* Two return statements in the mul() function */
int mul(int a, int b)
{
   if(a == 0 || b == 0)
   {
        return 0;
   }
   else
   {
        return (a * b);
   }
}

ANS:A - Representation of NULL pointer

No answer description is available. Let's discuss.

ANS:A - char p = *malloc(100);

No answer description is available. Let's discuss.

ANS:C - stdio.h and stddef.h

No answer description is available. Let's discuss.