Explanation:

Let's analyze the provided C++ program:

#include <stdio.h>

int main (void)
{
    int x, *p;
    x = 30;
    p = x;       // Error here
    printf("%d", *p);
    return 0;
}

In the given code:

• int x, *p; declares an integer x and a pointer to an integer p.
• x = 30; assigns the value 30 to x.
• p = x; attempts to assign the integer value x to the pointer p, which is incorrect.
• In C++, p should be assigned the address of x using p = &x;.

The line printf("%d", *p); attempts to print the value pointed to by p, but since p is not correctly assigned a valid address, this will result in an error.
Because p = x; is invalid in C++ (you cannot assign an integer directly to a pointer without casting or referencing), the program will not compile successfully and will result in a compilation error.

Thus, the correct answer is: Error