To answer this question, we need to understand the concept of input validation and the potential risks associated with not performing proper input validation.
Input validation is the process of verifying and validating user input to ensure that it meets certain criteria or constraints. It is an important security measure to prevent malicious or unexpected inputs from causing vulnerabilities in the code.
In this scenario, Tina is working on a multi-threaded application where users can specify the duration for which the threads may be put to sleep. If Tina does not perform any input validation, it means that she does not check or sanitize the user input for this duration.
The lack of input validation in this case can expose Tina's code to Denial of Service (DoS) attacks. A Denial of Service attack is a malicious attempt to disrupt the normal functioning of a system or network by overwhelming it with a flood of illegitimate requests or by exploiting vulnerabilities in the system.
By allowing users to specify an arbitrary duration for thread sleep without proper validation, an attacker could potentially input a very large or infinite duration, causing the threads to sleep for an extended period of time or indefinitely. This could lead to resource exhaustion, where the system becomes overwhelmed and unable to handle legitimate requests, ultimately causing a Denial of Service.
Therefore, the correct answer is C) Denial of Service.