Answer:
The function in Python:
def fizz_buzz_check(num):
 if num%3 == 0:
 result = "Fizz"
 if num%5 == 0:
 result = "Buzz"
 if num%3 == 0 and num%5 == 0:
 result = "FizzBuzz"
 if num%3 != 0 and num%5 != 0:
 result = num
 return result
Step-by-step explanation:
The function to complete is not given. So, I write a new function from scratch.
This defines the function
def fizz_buzz_check(num):
This checks if num is divisible by 3
 if num%3 == 0:
If yes, the returned value is stored as "Fizz"
 result = "Fizz"
This checks if num is divisible by 5
 if num%5 == 0:
If yes, the returned value is stored as "Buzz"
 result = "Buzz"
This checks if num is divisible by 3 and 5
 if num%3 == 0 and num%5 == 0:
If yes, the returned value is stored as "FizzBuzz"
 result = "FizzBuzz"
This checks if num is not divisible by 3 and by 5
 if num%3 != 0 and num%5 != 0:
If yes, the returned value is stored as the initial argument
 result = num
This returns the appropriate value
 return result