To determine which planets are likely to be inner planets, we first need to understand the concept of inner planets. Inner planets are typically those with orbital radii within 1 Astronomical Unit (AU) from the sun.
Given the orbital radii of the planets:
- Planet W: 5.2 AU
- Planet X: 0.72 AU
- Planet Y: 0.37 AU
- Planet Z: 19.1 AU
We will now evaluate the orbital radii to see which ones are less than 1 AU.
1. Planet W has an orbital radius of 5.2 AU: This is much greater than 1 AU, so Planet W is not an inner planet.
2. Planet X has an orbital radius of 0.72 AU: This is less than 1 AU, so Planet X is considered an inner planet.
3. Planet Y has an orbital radius of 0.37 AU: This is also less than 1 AU, so Planet Y is considered an inner planet.
4. Planet Z has an orbital radius of 19.1 AU: This is much greater than 1 AU, so Planet Z is not an inner planet.
Based on this analysis, Planets X and Y have orbital radii within 1 AU and are likely to be inner planets. Hence, the answer is:
[tex]\[
\boxed{X \text{ and } Y}
\][/tex]
