What do conditional statements do in a program?

Conditional statements are an essential control structure in programming that enable a program to execute different actions based on specific conditions. When a conditional statement is evaluated, such as an 'if' or 'switch' statement, it checks if a certain condition is true or false and directs the flow of execution accordingly. This allows for dynamic decision-making within the program, enabling it to respond differently based on user input, variable values, or other criteria.

For example, if a user inputs a valid password, the program may proceed to the next step. However, if the password is incorrect, the program can redirect the user to re-enter their credentials. This flexibility provided by conditional statements is crucial for creating interactive and responsive applications.

On the other hand, other options describe different aspects of programming. Ensuring that all code runs sequentially is more related to the general flow of execution without accounting for conditions. Synchronizing program runs pertains to managing multiple threads or processes, which is distinct from evaluating conditions. Optimizing performance usually involves improving the efficiency of code rather than altering the control flow based on specific conditions. Thus, the role of conditional statements is specifically to alter and direct execution flow, which is accurately captured in the choice regarding changing the flow of execution.