Answer the following question given this paragraph: For decades Pluto was a planet. But even then, scientists knew it was an unusual planet. The other outer planets are all gas giants. Pluto is small, icy and rocky. With a diameter of about 2400 kilometers, it has only about 1/5 the mass of Earth's Moon. The other planets orbit in a plane. Pluto's orbit is tilted. The shape of the orbit is like a long, narrow ellipse. Pluto's orbit is so elliptical that sometimes it is inside the orbit of Neptune. Q: Pluto's orbit is so elliptical that sometimes it is inside the orbit of which planet? Choices: - titan - Mars - Earth - neptune A:
A:
neptune