Solution

The correct answer is Option 4.

Key Points

• Global variables are variables that are declared outside of any function and can be accessed from any function within the same scope.
  • The values of the global variables which are sent to the called function may be changed inadvertently by the called function. This means that any function can modify the global variable, leading to potential side effects. (Option 1 is true)
  • Functions are supposed to be independent and isolated modules. This character is lost if they use global variables. Using global variables can lead to tightly coupled code, making the functions dependent on the state of global variables. (Option 2 is true)
  • It is not immediately apparent to the reader which values are being sent to the called function. This can make the code harder to read and understand as the dependencies are not explicit. (Option 3 is true)
  • A function that uses global variables does not suffer from reusability. This is the incorrect statement because functions using global variables indeed suffer from reusability as they rely on the global state. (Option 4 is not true)

Additional Information

• Global variables can lead to namespace pollution, where multiple variables may interfere with each other.
• They can make debugging difficult as any part of the code can change the global variable value.
• Global variables can be useful in certain scenarios, such as when maintaining state in a web application, but should be used sparingly and with caution.
• It is often better to use local variables or pass parameters explicitly to functions to maintain code clarity and modularity.