The correct answer is B. It orbits the Sun in regular intervals.
Halley's Comet (named after the astronomer Edmond Halley who first described it) is a comet that can be seen from Earth every 75 years. This comet differs from others because it has a regular and short orbital which makes it possible for astronomers to track the comet over time. Indeed, due to this pattern from ancient times people have observed and registered the appearance of the Halley's Comet. Additionally, like other comets, this is composed of dust, rocks, and ice. According to this, the statement that explains why Halley's Comet is unique is "It orbits the Sun in regular intervals".