Questions

Error occurs because we have mixed the ANSI prototype with K & R style of function definition.

When we use ANSI prototype for a function and pass a float to the function it is promoted to a double. When the function accepts this double into a float a type mismatch occurs hence the error.

The remedy for this error could be to define the function as :

int fun (float aa)

{

  ....

}

Here in the given options, Diamond is an element as it is the allotrope of the carbon atom.

This is a common error while compiling C program in Linux. This error occurs when you are using pthread_create function to create threads in your programs.

To fix this problem ensure following points:
Include header file pthread.h in your program.
Add –lpthread linker flag with compilation command.
1- Include Header file
#include <stdio.h>
#include <pthread.h>
...
...
2- Compile command
gcc main.c -o main -lpthread