Answer : 4. "Exoplanet"
Explanation :

Preliminary data from NASA's James Webb Space Telescope (JWST) suggests that there is a greater than 50% chance that exoplanet K2-18b contains dimethyl sulfide (DMS) gas. However, more analysis is needed before any definite conclusions can be reached. DMS is a gas produced only by living beings on Earth, primarily by phytoplankton in marine environments. The presence of DMS in K2-18b's atmosphere could be an unprecedented discovery, as the planet is believed to be covered in oceans and is 2.6 times larger than Earth.