What will happen if you try to add a duplicate value to a set?

When you attempt to add a duplicate value to a set in Python, the duplicate will be ignored, which is why that choice is correct.

Sets in Python are designed to contain unique elements. This means that when you try to add a value that already exists in the set, Python recognizes it as a duplicate and does not include it again. Therefore, the overall composition of the set remains unchanged.

For instance, if you create a set with the values {1, 2, 3} and then try to add the value 2 again, the set will simply remain as {1, 2, 3} after the attempted addition. The presence of the value 2 already makes it impossible for a set to include it again, upholding the principle of uniqueness.

While other choices suggest different behaviors, they do not accurately represent how sets operate in Python. For example, adding a duplicate does not cause a TypeError, nor does it create a situation where the existing value is overwritten as sets maintain only one instance of each value. This characteristic of sets makes them particularly useful when uniqueness is required in data management.