c language please

write a new raw one don't copy it from the internet

1- Write a recursion function to find the sum of all elements in the Fibonacci series with size =10; 2- Print the result of the Fibonacci series using recursion with fib(20); Ex: 0112358132134 3- Write a program in C to reverse a string using recursion. 4- Write a program in C to get the largest element of an array using recursion