Which basic control flow construct is characterized by executing code repeatedly based on a specified condition?

The correct answer is iteration. In programming and software testing, iteration refers to the repetition of code execution as long as a specified condition remains true. This is fundamental in scenarios where the same set of instructions needs to be executed multiple times until a particular condition changes, such as processing items in a list or repeating a task until a user gives a specific input.

Iteration allows for efficient and concise code, enabling developers to handle repetitive tasks without needing to manually write out similar blocks of code for each execution. Common structures that facilitate iteration include loops such as "for," "while," and "do-while."

In contrast, a decision point refers to branching logic where the program chooses a path based on a condition, but it does not involve repeated execution of code. Sequence simply denotes the linear execution of statements one after another, and the case statement serves as a control structure for selecting one of many possible code paths but does not involve repetition based on conditions. Thus, iteration stands out as the construct specifically designed for executing a piece of code repeatedly contingent upon defined criteria.