Explanation:

- Correct Answer: Option 3 - Juno

- NASA's Juno spacecraft has been orbiting and studying Jupiter since July 4, 2016. The mission aims to understand Jupiter's composition, gravity field, magnetic field, and polar magnetosphere, among other scientific objectives.

- Option 1: Muno

- This option is incorrect. There is no NASA spacecraft known as Muno that is associated with the study of Jupiter.

- Option 2: Bruno

- This option is incorrect. Bruno is not the name of any NASA spacecraft involved in the Jupiter mission.

- Option 4: Luno

- This option is incorrect as well. Luno is not associated with NASA's missions concerning Jupiter.