Explanation:

All codes are correct.
Key Findings of Chandrayaan-2 Orbiter

• Detection of Argon-40: The mass spectrometer CHandra's Atmospheric Compositional Explorer 2 (CHACE 2) conducted first-ever in-situ study of the composition of the lunar neutral exosphere from a polar orbital platform.
• It detected and studied the variability of the Argon-40 at the middle and higher latitudes of the Moon, depicting the radiogenic activities in the mid and higher latitudes of the Lunar interior. 
• Detection of Chromium and Manganese: Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS) payload has detected minor elements of chromium and manganese through remote sensing. 
• Observations of Microflares of the Sun: The observations of microflares of the Sun, during the quiet-Sun period, which provide important clues on the coronal heating problem of the Sun, were made by the Solar X-ray Monitor (XSM) payload.
• Detection of the Hydration Features: The first-ever unambiguous detection of the hydration features of the Moon was achieved by Chandrayaan-2 with its Imaging Infra-Red Spectrometer (IIRS) payload, which captured clear signatures of Hydroxyl and water-ice on the lunar surface.
• Detection of the Subsurface Water-ice: The Dual Frequency Synthetic Aperture Radar (DFSAR) instrument detected signatures of the subsurface water-ice, and achieved high resolution mapping of the lunar morphological features in the polar regions.
• Imaging the Moon: Imaging the moon from 100 km lunar orbit with "best-ever" achieved resolution of 25 cm with its Orbiter High Resolution Camera (OHRC).
• Geological Findings: The Terrain Mapping Camera (TMC 2) of Chandrayaan-2, which is conducting imaging of the Moon at a global scale, has found interesting geologic signatures of lunar crustal shortening, and identification of volcanic domes.
• Study of Moon's Ionosphere: The Dual Frequency Radio Science (DFRS) experiment onboard Chandrayaan-2 has studied the ionosphere of the Moon, which is generated by the solar photo-ionisation of the neutral species of the lunar exosphere.

Hence option 4th is correct.