Final answer:
Multithreading an interactive program increases responsiveness by continuing to run even if a part of it is blocked.
Step-by-step explanation:
The correct answer is a) Continuing to run even if a part of it is blocked. Multithreading an interactive program allows it to run simultaneous tasks or threads. This means that if one part of the program is blocked or waiting for a resource, other parts of the program can continue running, increasing responsiveness to the user.