In the context of the solar system, the gaseous giants are Jupiter, Saturn, Uranus, and Neptune.
Based on their positions:
- W: Closest to the Sun (Mercury, a rocky planet)
- X: 4th from the Sun (Mars, a rocky planet)
- Y: 7th from the Sun (Uranus, a gaseous giant)
- Z: Last and farthest from the Sun (Neptune, a gaseous giant)
Since both Y and Z are gaseous giants, Y is explicitly the 7th from the Sun and is a gaseous giant in this scenario.
Therefore, the object that is a gaseous giant is Y.