The special effect where time appears to have decreased is known as slow motion. Slow motion is a technique used in film-making and photography to capture a specific moment at a much slower rate than it was originally recorded. This effect allows viewers to see details that might have been missed at normal speed and adds a dramatic or artistic element to the visual presentation.
In slow motion, the action appears to be moving at a fraction of its actual speed, giving it a smooth and graceful look. This effect is achieved by recording footage at a higher frame rate than usual and then playing it back at a standard frame rate, which creates the illusion of slowed-down motion.
Therefore, in the context of the given choices, the correct answer is b. slow motion. This option best describes the special effect where time appears to have decreased, as it aligns with the technique used to achieve the desired visual effect in films and videos.